103 DBMS_STATS

Using DBMS_STATS

This section contains topics which relate to using the DBMS_STATS package.

• Overview

• Types

• Constants

• Operational Notes

• Deprecated Subprograms

• Examples

---

Overview

The Oracle RDBMS allows you to collect statistics of many different kinds as an aid to to improving performance. This package is concerned with optimizer statistics only. Given that Oracle sets automatic statistics collection of this kind on by default, this package is intended for only specialized cases.

The statistics of interest to be viewed or modified can reside in the dictionary or in a table created in the user's schema for this purpose. You can also collect and manage user-defined statistics for tables and domain indexes using this package.

For example, if the DELETE_COLUMN_STATS procedure is invoked on a column for which an association is defined, user-defined statistics for that column are deleted in addition to deletion of the standard statistics.

Only statistics stored in the dictionary have an impact on the cost-based optimizer. You can also use DBMS_STATS to gather statistics in parallel

---

Types

Types for the minimum and maximum values and histogram endpoints include:

TYPE numarray  IS VARRAY(256) OF NUMBER;
TYPE datearray IS VARRAY(256) OF DATE;
TYPE chararray IS VARRAY(256) OF VARCHAR2(4000);
TYPE rawarray  IS VARRAY(256) OF RAW(2000);
TYPE fltarray IS VARRAY(256) OF BINARY_FLOAT;
TYPE dblarray IS VARRAY(256) OF BINARY_DOUBLE;
 
TYPE StatRec IS RECORD (
  epc    NUMBER,
  minval RAW(2000),
  maxval RAW(2000),
  bkvals NUMARRAY,
  novals NUMARRAY);
 

Types for listing stale tables include:

TYPE ObjectElem IS RECORD (
  ownname     VARCHAR2(30),     -- owner
  objtype     VARCHAR2(6),      -- 'TABLE' or 'INDEX'
  objname     VARCHAR2(30),     -- table/index
  partname    VARCHAR2(30),     -- partition
  subpartname VARCHAR2(30),     -- subpartition
  confidence  NUMBER);          -- not used
type ObjectTab is TABLE of ObjectElem;

---

Constants

Use the following constant to indicate that auto-sample size algorithms should be used:

AUTO_SAMPLE_SIZE CONSTANT NUMBER;

The constant used to determine the system default degree of parallelism, based on the initialization parameters, is:

DEFAULT_DEGREE CONSTANT NUMBER;

Use the following constant to let Oracle select the degree of parallelism based on size of the object, number of CPUs and initialization parameters:

AUTO_DEGREE CONSTANT NUMBER;

Use the following constant to let Oracle decide whether to collect statistics for indexes or not:

AUTO_CASCADE CONSTANT BOOLEAN;

Use the following constant to let oracle decide when to invalidate dependent cursors.

AUTO_INVALIDATE CONSTANT BOOLEAN

---

Operational Notes

The DBMS_STATS subprograms perform the following general operations:

• Gathering Optimizer Statistics

• Setting or Getting Statistics

• Deleting Statistics

• Transferring Statistics

• Locking or Unlocking Statistics

• Restoring and Purging Statistics History

• User-Defined Statistics

Most of the DBMS_STATS procedures include the three parameters statown, stattab, and statid. These parameters allow you to store statistics in your own tables (outside of the dictionary), which does not affect the optimizer. Therefore, you can maintain and experiment with sets of statistics.

The stattab parameter specifies the name of a table in which to hold statistics, and it is assumed that it resides in the same schema as the object for which statistics are collected (unless the statown parameter is specified). You can create multiple tables with different stattab identifiers to hold separate sets of statistics.

Additionally, you can maintain different sets of statistics within a single stattab by using the statid parameter, which avoids cluttering the user's schema.

For the SET and GET procedures, if stattab is not provided (that is, NULL), then the operation works directly on the dictionary statistics; therefore, you do not need to create these statistics tables if they only plan to modify the dictionary directly. However, if stattab is not NULL, then the SET or GET operation works on the specified user statistics table, and not the dictionary.

You can change the default values of some of the parameters of DBMS_STATS procedures using the SET_PARAM Procedure.

Most of the procedures in this package commit the current transaction, perform the operation, and then commit again.

Most of the procedures have a parameter, force which allows you to override any lock on statistics.Whenever statistics in dictionary are modified, old versions of statistics are saved automatically for future restoring.

Gathering Optimizer Statistics

Use the following subprograms to gather certain classes of optimizer statistics, with possible performance improvements over the ANALYZE command:

GATHER_DATABASE_STATS Procedures
GATHER_DICTIONARY_STATS Procedure
GATHER_FIXED_OBJECTS_STATS Procedure
GATHER_INDEX_STATS Procedure
GATHER_SCHEMA_STATS Procedures
GATHER_SYSTEM_STATS Procedure
GATHER_TABLE_STATS Procedure

The GATHER_* procedures also collect user-defined statistics for columns and domain indexes.

The statown, stattab, and statid parameters instruct the package to back up current statistics in the specified table before gathering new statistics.

Oracle also provides the following procedure for generating statistics for derived objects when you have sufficient statistics on related objects:

GENERATE_STATS Procedure

Setting or Getting Statistics

Use the following subprograms to store and retrieve individual column-related, index-related, and table-related statistics:

PREPARE_COLUMN_VALUES Procedures
PREPARE_COLUMN_VALUES_NVARCHAR2 Procedure
PREPARE_COLUMN_VALUES_ROWID Procedure

SET_COLUMN_STATS Procedures
SET_INDEX_STATS Procedures
SET_SYSTEM_STATS Procedure
SET_TABLE_STATS Procedure

GET_COLUMN_STATS Procedures
GET_INDEX_STATS Procedures
GET_SYSTEM_STATS Procedure
GET_TABLE_STATS Procedure

In the special versions of the SET_*_STATS procedures for setting user-defined statistics, the following, if provided, are stored in the dictionary or external statistics table:

• User-defined statistics (extstats)

• The statistics type schema name (statsschema)

• The statistics type name (statsname)

The user-defined statistics and the corresponding statistics type are inserted into the USTATS$ dictionary table. You can specify user-defined statistics without specifying the statistics type name.

The special versions of the GET_*_STATS procedures return user-defined statistics and the statistics type owner and name as OUT arguments corresponding to the schema object specified. If user-defined statistics are not collected, NULL values are returned.

Deleting Statistics

The DELETE_* procedures delete both user-defined statistics and the standard statistics for the given schema object.

DELETE_COLUMN_STATS Procedure
DELETE_DATABASE_STATS Procedure
DELETE_DICTIONARY_STATS Procedure
DELETE_FIXED_OBJECTS_STATS Procedure
DELETE_INDEX_STATS Procedure
DELETE_SCHEMA_STATS Procedure
DELETE_SYSTEM_STATS Procedure
DELETE_TABLE_STATS Procedure

Transferring Statistics

Use the following procedures for creating and dropping the user statistics table.

CREATE_STAT_TABLE Procedure
DROP_STAT_TABLE Procedure

Use the following procedures to transfer statistics

• from the dictionary to a user statistics table (EXPORT_*)

• from a user statistics table to the dictionary (IMPORT_*)

EXPORT_COLUMN_STATS Procedure
EXPORT_DATABASE_STATS Procedure
EXPORT_DICTIONARY_STATS Procedure
EXPORT_FIXED_OBJECTS_STATS Procedure
EXPORT_INDEX_STATS Procedure
EXPORT_SCHEMA_STATS Procedure
EXPORT_SYSTEM_STATS Procedure
EXPORT_TABLE_STATS Procedure

IMPORT_COLUMN_STATS Procedure
IMPORT_DATABASE_STATS Procedure
IMPORT_DICTIONARY_STATS Procedure
IMPORT_FIXED_OBJECTS_STATS Procedure
IMPORT_INDEX_STATS Procedure
IMPORT_SCHEMA_STATS Procedure
IMPORT_SYSTEM_STATS Procedure
IMPORT_TABLE_STATS Procedure

Locking or Unlocking Statistics

Use the following procedures to lock and unlock statistics on objects.

LOCK_SCHEMA_STATS Procedure
LOCK_TABLE_STATS Procedure

UNLOCK_SCHEMA_STATS Procedure
UNLOCK_TABLE_STATS Procedure

The LOCK_* procedures either freeze the current set of the statistics or to keep the statistics empty (uncollected).When statistics on a table are locked, all the statistics depending on the table, including table statistics, column statistics, histograms and statistics on all dependent indexes, are considered to be locked.

Restoring and Purging Statistics History

Use the following procedures to restore statistics as of a specified timestamp. This is useful in case newly collected statistics leads to some sub-optimal execution plans and the administrator wants to revert to the previous set of statistics.

RESET_PARAM_DEFAULTS Procedure
RESTORE_DICTIONARY_STATS Procedure
RESTORE_FIXED_OBJECTS_STATS Procedure
RESTORE_SCHEMA_STATS Procedure
RESTORE_SYSTEM_STATS Procedure
RESTORE_TABLE_STATS Procedure

Whenever statistics in dictionary are modified, old versions of statistics are saved automatically for future restoring. The old statistics are purged automatically at regular intervals based on the statistics history retention setting and the time of recent statistics gathering performed in the system. Retention is configurable using the ALTER_STATS_HISTORY_RETENTION Procedure.

The other DBMS_STATS procedures related to restoring statistics are:

• PURGE_STATS Procedure: This procedure lets you manually purge old versions beyond a time stamp.

• GET_STATS_HISTORY_RETENTION Function: This function gets the current statistics history retention value.

• GET_STATS_HISTORY_AVAILABILITY Function: This function gets the oldest time stamp where statistics history is available. Users cannot restore statistics to a time stamp older than the oldest time stamp.

RESTORE_* operations are not supported for user defined statistics.

User-Defined Statistics

The DBMS_STATS package supports operations on user-defined statistics. When a domain index or column is associated with a statistics type (using the associate statement), operations on the index or column manipulate user-defined statistics. For example, gathering statistics for a domain index (for which an association with a statistics type exists) using the GET_INDEX_STATS Procedures invokes the user-defined statistics collection method of the associated statistics type. Similarly, delete, transfer, import, and export operations manipulate user-defined statistics.

SET_* and GET_* operations for user-defined statistics are also supported using a special version of the SET and GET interfaces for columns and indexes.

EXPORT_*, IMPORT_* and RESTORE_* operations are not supported for user defined statistics.

---

Deprecated Subprograms

The following subprograms are obsolete with Release 10g:

• ALTER_DATABASE_TAB_MONITORING Procedure

• ALTER_SCHEMA_TAB_MONITORING Procedure

In earlier releases, you could use these subprograms to change DML monitoring behavior. These subprograms are now non-operational because Oracle performs their functions automatically.

---

Examples

• Saving Original Statistics and Gathering New Statistics

• Gathering Daytime System Statistics

Saving Original Statistics and Gathering New Statistics

Assume many modifications have been made to the employees table since the last time statistics were gathered. To ensure that the cost-based optimizer is still picking the best plan, statistics should be gathered once again; however, the user is concerned that new statistics will cause the optimizer to choose bad plans when the current ones are acceptable. The user can do the following:

BEGIN
   DBMS_STATS.CREATE_STAT_TABLE ('hr', 'savestats');
   DBMS_STATS.GATHER_TABLE_STATS ('hr', 'employees', stattab => 'savestats');
END;

This operation gathers new statistics on the employees table, but first saves the original statistics in a user statistics table: hr.savestats.

If the user believes that the new statistics are causing the optimizer to generate poor plans, then the original statistics can be restored as follows:

BEGIN
   DBMS_STATS.DELETE_TABLE_STATS ('hr', 'employees');
   DBMS_STATS.IMPORT_TABLE_STATS ('hr', 'employees', stattab => 'savestats');
END;

Gathering Daytime System Statistics

Assume that you want to perform database application processing OLTP transactions during the day and run reports at night.

To collect daytime system statistics, gather statistics for 720 minutes. Store the statistics in the MYSTATS table.

BEGIN
   DBMS_STATS.GATHER_SYSTEM_STATS (
      interval => 720,
      stattab  => 'mystats',
      statid   => 'OLTP');
END;

To collect nighttime system statistics, gather statistics for 720 minutes. Store the statistics in the MYSTATS table.

BEGIN
   DBMS_STATS.GATHER_SYSTEM_STATS (
      interval => 720,
      stattab  => 'mystats',
      statid   => 'OLAP');
END;

Update the dictionary with the gathered statistics.

VARIABLE   jobno   number;
BEGIN
   DBMS_JOB.SUBMIT (:jobno, 'DBMS_STATS.IMPORT_SYSTEM_STATS
   (''mystats'',''OLTP'');'
   sysdate, 'sysdate + 1');
   COMMIT;
END;

BEGIN
   DBMS_JOB.SUBMIT (:jobno, 'DBMS_STATS.IMPORT_SYSTEM_STATS
   (''mystats'',''OLAP'');'
   sysdate + 0.5, 'sysdate + 1');
   COMMIT;
END;

Summary of DBMS_STATS Subprograms

---

ALTER_DATABASE_TAB_MONITORING Procedure

This procedure enables or disables the DML monitoring feature of all the tables in the schema, except for snapshot logs and the tables, which monitoring does not support. Using this procedure is equivalent to issuing ALTER TABLE...MONITORING (or NOMONITORING) individually.

Syntax

DBMS_STATS.ALTER_DATABASE_TAB_MONITORING (
   monitoring BOOLEAN DEFAULT TRUE,
   sysobjs    BOOLEAN DEFAULT FALSE);

Parameters

Exceptions

ORA-20000: Insufficient privileges.

---

ALTER_SCHEMA_TAB_MONITORING Procedure

This procedure enables or disables the DML monitoring feature of all the tables in the schema, except for snapshot logs and the tables, which monitoring does not support. Using this procedure is equivalent to issuing ALTER TABLE...MONITORING (or NOMONITORING) individually.

Syntax

DBMS_STATS.ALTER_SCHEMA_TAB_MONITORING (
   ownname    VARCHAR2 DEFAULT NULL,
   monitoring BOOLEAN DEFAULT TRUE);

Parameters

Usage Notes

You should enable monitoring if you use GATHER_DATABASE_STATS or GATHER_SCHEMA_STATS with the GATHER AUTO or GATHER STALE options.

Exceptions

ORA-20000: Insufficient privileges.

---

ALTER_STATS_HISTORY_RETENTION Procedure

This procedure changes the statistics history retention value. Statistics history retention is used by both the automatic purge and PURGE_STATS Procedure.

Syntax

DBMS_STATS.ALTER_STATS_HISTORY_RETENTION (
   retention       IN     NUMBER);

Parameters

Usage Notes

To run this procedure, you must have the SYSDBA or both ANALYZE ANY DICTIONARY and ANALYZE ANY system privilege.

Exceptions

ORA-20000: Insufficient privileges.

---

CONVERT_RAW_VALUE Procedures

This procedure converts the internal representation of a minimum or maximum value into a datatype-specific value. The minval and maxval fields of the StatRec structure as filled in by GET_COLUMN_STATS or PREPARE_COLUMN_VALUES are appropriate values for input.

Syntax

DBMS_STATS.CONVERT_RAW_VALUE (
   rawval     RAW, 
   resval OUT BINARY_FLOAT);

DBMS_STATS.CONVERT_RAW_VALUE (
   rawval     RAW, 
   resval OUT BINARY_DOUBLE);

DBMS_STATS.CONVERT_RAW_VALUE (
   rawval     RAW, 
   resval OUT DATE);

DBMS_STATS.CONVERT_RAW_VALUE (
   rawval     RAW, 
   resval OUT NUMBER);

DBMS_STATS.CONVERT_RAW_VALUE (
   rawval     RAW, 
   resval OUT VARCHAR2);

Pragmas

pragma restrict_references(convert_raw_value, WNDS, RNDS, WNPS, RNPS);

Parameters

---

CONVERT_RAW_VALUE_NVARCHAR Procedure

This procedure converts the internal representation of a minimum or maximum value into a datatype-specific value. The minval and maxval fields of the StatRec structure as filled in by GET_COLUMN_STATS or PREPARE_COLUMN_VALUES are appropriate values for input.

Syntax

DBMS_STATS.CONVERT_RAW_VALUE_NVARCHAR (
   rawval     RAW, 
   resval OUT NVARCHAR2);

Pragmas

pragma restrict_references(convert_raw_value_nvarchar, WNDS, RNDS, WNPS, RNPS);

Parameters

---

CONVERT_RAW_VALUE_ROWID Procedure

This procedure converts the internal representation of a minimum or maximum value into a datatype-specific value. The minval and maxval fields of the StatRec structure as filled in by GET_COLUMN_STATS or PREPARE_COLUMN_VALUES are appropriate values for input.

Syntax

DBMS_STATS.CONVERT_RAW_VALUE_ROWID (
   rawval     RAW, 
   resval OUT ROWID);

Pragmas

pragma restrict_references(convert_raw_value_rowid, WNDS, RNDS, WNPS, RNPS);

Parameters

---

CREATE_STAT_TABLE Procedure

This procedure creates a table with name stattab in ownname's schema which is capable of holding statistics. The columns and types that compose this table are not relevant as it should be accessed solely through the procedures in this package.

Syntax

DBMS_STATS.CREATE_STAT_TABLE (
   ownname  VARCHAR2, 
   stattab  VARCHAR2,
   tblspace VARCHAR2 DEFAULT NULL);

Parameters

Exceptions

ORA-20000: Table already exists or insufficient privileges.

ORA-20001: Tablespace does not exist.

---

DELETE_COLUMN_STATS Procedure

This procedure deletes column-related statistics.

Syntax

DBMS_STATS.DELETE_COLUMN_STATS (
   ownname       VARCHAR2, 
   tabname       VARCHAR2, 
   colname       VARCHAR2, 
   partname      VARCHAR2 DEFAULT NULL,
   stattab       VARCHAR2 DEFAULT NULL, 
   statid        VARCHAR2 DEFAULT NULL,
   cascade_parts BOOLEAN  DEFAULT TRUE,
   statown       VARCHAR2 DEFAULT NULL,
   no_invalidate BOOLEAN  DEFAULT to_no_invalidate_type (
                                     get_param('NO_INVALIDATE')),
   force         BOOLEAN DEFAULT FALSE);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20005: Object statistics are locked.

---

DELETE_DATABASE_STATS Procedure

This procedure deletes statistics for all the tables in a database.

Syntax

DBMS_STATS.DELETE_DATABASE_STATS (
   stattab          VARCHAR2 DEFAULT NULL, 
   statid           VARCHAR2 DEFAULT NULL,
   statown          VARCHAR2 DEFAULT NULL,
   no_invalidate    BOOLEAN  DEFAULT to_no_invalidate_type (
                                     get_param('NO_INVALIDATE')),
   force            BOOLEAN  DEFAULT FALSE);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

---

DELETE_DICTIONARY_STATS Procedure

This procedure deletes statistics for all dictionary schemas ('SYS', 'SYSTEM' and RDBMS component schemas).

Syntax

DBMS_STATS.DELETE_DICTIONARY_STATS (
   stattab          VARCHAR2 DEFAULT NULL, 
   statid           VARCHAR2 DEFAULT NULL,
   statown          VARCHAR2 DEFAULT NULL,
   no_invalidate    BOOLEAN  DEFAULT to_no_invalidate_type (
                                     get_param('NO_INVALIDATE')),
   force            BOOLEAN  DEFAULT FALSE);

Parameters

Usage Notes

You must have the SYSDBA or both ANALYZE ANY DICTIONARY and ANALYZE ANY system privilege to execute this procedure.

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20002: Bad user statistics table, may need to upgrade it.

---

DELETE_FIXED_OBJECTS_STATS Procedure

This procedure deletes statistics of all fixed tables.

Syntax

DBMS_STATS.DELETE_FIXED_OBJECTS_STATS (
   stattab        VARCHAR2 DEFAULT NULL,
   statid         VARCHAR2 DEFAULT NULL,
   statown        VARCHAR2 DEFAULT NULL, 
   no_invalidate  BOOLEAN  DEFAULT to_no_invalidate_type (
                                     get_param('NO_INVALIDATE')),
   force          BOOLEAN  DEFAULT FALSE); 

Parameters

Usage Notes

You must have the SYSDBA or ANALYZE ANY DICTIONARY system privilege to execute this procedure.

Exceptions

ORA-20000: Insufficient privileges.

ORA-20002: Bad user statistics table, may need to upgrade it.

---

DELETE_INDEX_STATS Procedure

This procedure deletes index-related statistics.

Syntax

DBMS_STATS.DELETE_INDEX_STATS (
   ownname          VARCHAR2, 
   indname          VARCHAR2,
   partname         VARCHAR2 DEFAULT NULL,
   stattab          VARCHAR2 DEFAULT NULL, 
   statid           VARCHAR2 DEFAULT NULL,
   cascade_parts    BOOLEAN  DEFAULT TRUE,
   statown          VARCHAR2 DEFAULT NULL,
   no_invalidate    BOOLEAN  DEFAULT to_no_invalidate_type (
                                     get_param('NO_INVALIDATE')),
   force            BOOLEAN DEFAULT FALSE);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20005: Object statistics are locked.

---

DELETE_SCHEMA_STATS Procedure

This procedure deletes statistics for an entire schema.

Syntax

DBMS_STATS.DELETE_SCHEMA_STATS (
   ownname          VARCHAR2, 
   stattab          VARCHAR2 DEFAULT NULL, 
   statid           VARCHAR2 DEFAULT NULL,
   statown          VARCHAR2 DEFAULT NULL,
   no_invalidate    BOOLEAN DEFAULT to_no_invalidate_type (
                                     get_param('NO_INVALIDATE')),
   force            BOOLEAN DEFAULT FALSE);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges

---

DELETE_SYSTEM_STATS Procedure

This procedure deletes workload statistics (collected using the 'INTERVAL' or 'START' and 'STOP' options) and resets the default to noworkload statistics (collected using 'NOWORKLOAD' option) if stattab is not specified. If stattab is specified, the subprogram deletes all system statistics with the associated statid from the stattab.

Syntax

DBMS_STATS.DELETE_SYSTEM_STATS (
   stattab       VARCHAR2 DEFAULT NULL, 
   statid        VARCHAR2 DEFAULT NULL,
   statown       VARCHAR2 DEFAULT NULL);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20002: Bad user statistics table; may need to be upgraded.

---

DELETE_TABLE_STATS Procedure

This procedure deletes table-related statistics.

Syntax

DBMS_STATS.DELETE_TABLE_STATS (
   ownname          VARCHAR2, 
   tabname          VARCHAR2, 
   partname         VARCHAR2 DEFAULT NULL,
   stattab          VARCHAR2 DEFAULT NULL, 
   statid           VARCHAR2 DEFAULT NULL,
   cascade_parts    BOOLEAN  DEFAULT TRUE, 
   cascade_columns  BOOLEAN  DEFAULT TRUE,
   cascade_indexes  BOOLEAN  DEFAULT TRUE,
   statown          VARCHAR2 DEFAULT NULL,
   no_invalidate    BOOLEAN  DEFAULT to_no_invalidate_type (
                                     get_param('NO_INVALIDATE')),
   force            BOOLEAN DEFAULT FALSE);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20005: Object statistics are locked.

---

DROP_STAT_TABLE Procedure

This procedure drops a user statistics table.

Syntax

DBMS_STATS.DROP_STAT_TABLE (
   ownname VARCHAR2, 
   stattab VARCHAR2);

Parameters

Exceptions

ORA-20000: Table does not exists or insufficient privileges.

---

EXPORT_COLUMN_STATS Procedure

This procedure retrieves statistics for a particular column and stores them in the user statistics table identified by stattab.

Syntax

DBMS_STATS.EXPORT_COLUMN_STATS (
   ownname  VARCHAR2, 
   tabname  VARCHAR2, 
   colname  VARCHAR2, 
   partname VARCHAR2 DEFAULT NULL,
   stattab  VARCHAR2, 
   statid   VARCHAR2 DEFAULT NULL,
   statown  VARCHAR2 DEFAULT NULL);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

---

EXPORT_DATABASE_STATS Procedure

This procedure retrieves statistics for all objects in the database and stores them in the user statistics tables identified by statown.stattab.

Syntax

DBMS_STATS.EXPORT_DATABASE_STATS (
   stattab VARCHAR2, 
   statid  VARCHAR2 DEFAULT NULL,
   statown VARCHAR2 DEFAULT NULL);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

---

EXPORT_DICTIONARY_STATS Procedure

This procedure retrieves statistics for all dictionary schemas ('SYS', 'SYSTEM' and RDBMS component schemas) and stores them in the user statistics table identified by stattab.

Syntax

DBMS_STATS.EXPORT_DICTIONARY_STATS (
   stattab VARCHAR2, 
   statid  VARCHAR2 DEFAULT NULL,
   statown VARCHAR2 DEFAULT NULL);

Parameters

Usage Notes

You must have the SYSDBA or ANALYZE ANY DICTIONARY and ANALYZE ANY system privilege to execute this procedure.

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20002: Bad user statistics table, may need to upgrade it.

---

EXPORT_FIXED_OBJECTS_STATS Procedure

This procedure retrieves statistics for fixed tables and stores them in the user statistics table identified by stattab.

Syntax

DBMS_STATS.EXPORT_FIXED_OBJECTS_STATS (
   stattab  VARCHAR2, 
   statid   VARCHAR2 DEFAULT NULL,
   statown  VARCHAR2 DEFAULT NULL);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20002: Bad user statistics table, may need to upgrade it.

---

EXPORT_INDEX_STATS Procedure

This procedure retrieves statistics for a particular index and stores them in the user statistics table identified by stattab.

Syntax

DBMS_STATS.EXPORT_INDEX_STATS (
   ownname  VARCHAR2, 
   indname  VARCHAR2, 
   partname VARCHAR2 DEFAULT NULL,
   stattab  VARCHAR2, 
   statid   VARCHAR2 DEFAULT NULL,
   statown  VARCHAR2 DEFAULT NULL);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

---

EXPORT_SCHEMA_STATS Procedure

This procedure retrieves statistics for all objects in the schema identified by ownname and stores them in the user statistics tables identified by stattab.

Syntax

DBMS_STATS.EXPORT_SCHEMA_STATS (
   ownname VARCHAR2,
   stattab VARCHAR2, 
   statid  VARCHAR2 DEFAULT NULL,
   statown VARCHAR2 DEFAULT NULL);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

---

EXPORT_SYSTEM_STATS Procedure

This procedure retrieves system statistics and stores them in the user statistics table, identified by stattab.

Syntax

DBMS_STATS.EXPORT_SYSTEM_STATS (
   stattab       VARCHAR2, 
   statid        VARCHAR2 DEFAULT NULL,
   statown       VARCHAR2 DEFAULT NULL);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20002: Bad user statistics table; may need to be upgraded.

ORA-20003: Unable to export system statistics.

---

EXPORT_TABLE_STATS Procedure

This procedure retrieves statistics for a particular table and stores them in the user statistics table. Cascade results in all index and column statistics associated with the specified table being exported as well.

Syntax

DBMS_STATS.EXPORT_TABLE_STATS (
   ownname  VARCHAR2, 
   tabname  VARCHAR2, 
   partname VARCHAR2 DEFAULT NULL,
   stattab  VARCHAR2, 
   statid   VARCHAR2 DEFAULT NULL,
   cascade  BOOLEAN  DEFAULT TRUE,
   statown  VARCHAR2 DEFAULT NULL);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

---

FLUSH_DATABASE_MONITORING_INFO Procedure

This procedure flushes in-memory monitoring information for all tables in the dictionary. Corresponding entries in the *_TAB_MODIFICATIONS, *_TAB_STATISTICS and *_IND_STATISTICS views are updated immediately, without waiting for the Oracle database to flush them periodically. This procedure is useful when you need up-to-date information in those views. Because the GATHER_*_STATS procedures internally flush monitoring information, it is not necessary to run this procedure before gathering the statistics.

Syntax

DBMS_STATS.FLUSH_DATABASE_MONITORING_INFO; 

Exceptions

ORA-20000: Insufficient privileges.

---

GATHER_DATABASE_STATS Procedures

This procedure gathers statistics for all objects in the database.

Syntax

DBMS_STATS.GATHER_DATABASE_STATS (
   estimate_percent NUMBER   DEFAULT to_estimate_percent_type 
                                                (get_param('ESTIMATE_PERCENT')),
   block_sample     BOOLEAN  DEFAULT FALSE,
   method_opt       VARCHAR2 DEFAULT get_param('METHOD_OPT'),
   degree           NUMBER   DEFAULT to_degree_type(get_param('DEGREE')),
   granularity      VARCHAR2 DEFAULT GET_PARAM('GRANULARITY'), 
   cascade          BOOLEAN  DEFAULT to_cascade_type(get_param('CASCADE')),
   stattab          VARCHAR2 DEFAULT NULL, 
   statid           VARCHAR2 DEFAULT NULL,
   options          VARCHAR2 DEFAULT 'GATHER',
   objlist          OUT      ObjectTab,
   statown          VARCHAR2 DEFAULT NULL,
   gather_sys       BOOLEAN  DEFAULT TRUE,
   no_invalidate    BOOLEAN  DEFAULT to_no_invalidate_type (
                                     get_param('NO_INVALIDATE')));

DBMS_STATS.GATHER_DATABASE_STATS (
   estimate_percent NUMBER   DEFAULT to_estimate_percent_type 
                                                (get_param('ESTIMATE_PERCENT')), 
   block_sample     BOOLEAN  DEFAULT FALSE,
   method_opt       VARCHAR2 DEFAULT get_param('METHOD_OPT'),
   degree           NUMBER   DEFAULT to_degree_type(get_param('DEGREE')),
   granularity      VARCHAR2 DEFAULT GET_PARAM('GRANULARITY'), 
   cascade          BOOLEAN  DEFAULT to_cascade_type(get_param('CASCADE')),
   stattab          VARCHAR2 DEFAULT NULL, 
   statid           VARCHAR2 DEFAULT NULL,
   options          VARCHAR2 DEFAULT 'GATHER',
   statown          VARCHAR2 DEFAULT NULL,
   gather_sys       BOOLEAN  DEFAULT TRUE,
   no_invalidate    BOOLEAN  DEFAULT to_no_invalidate_type (
                                     get_param('NO_INVALIDATE')));

Parameters

Usage Notes

Statistics for external tables are not collected by this procedure.

Exceptions

ORA-20000: Insufficient privileges.

ORA-20001: Bad input value.

---

GATHER_DICTIONARY_STATS Procedure

This procedure gathers statistics for dictionary schemas 'SYS', 'SYSTEM' and schemas of RDBMS components.

Syntax

DBMS_STATS.GATHER_DICTIONARY_STATS (
   comp_id          VARCHAR2 DEFAULT NULL, 
   estimate_percent NUMBER   DEFAULT to_estimate_percent_type 
                                                (get_param('ESTIMATE_PERCENT')),
   block_sample     BOOLEAN  DEFAULT FALSE,
   method_opt       VARCHAR2 DEFAULT get_param('METHOD_OPT'),
   degree           NUMBER   DEFAULT to_degree_type(get_param('DEGREE')),
   granularity      VARCHAR2 DEFAULT GET_PARAM('GRANULARITY'),
   cascade          BOOLEAN  DEFAULT to_cascade_type(get_param('CASCADE')),
   stattab          VARCHAR2 DEFAULT NULL, 
   statid           VARCHAR2 DEFAULT NULL,
   options          VARCHAR2 DEFAULT 'GATHER AUTO', 
   objlist    OUT   ObjectTab,
   statown          VARCHAR2 DEFAULT NULL,
   no_invalidate    BOOLEAN  DEFAULT to_no_invalidate_type (
                                     get_param('NO_INVALIDATE')));

DBMS_STATS.GATHER_DICTIONARY_STATS (
   comp_id           VARCHAR2 DEFAULT NULL,
   estimate_percent  NUMBER DEFAULT 
                          to_estimate_percent_type(GET_PARAM('ESTIMATE_PERCENT')),
   block_sample      BOOLEAN DEFAULT FALSE,
   method_opt        VARCHAR2 DEFAULT GET_PARAM('METHOD_OPT'),
   degree            NUMBER DEFAULT to_degree_type(GET_PARAM('DEGREE')),
   granularity       VARCHAR2 DEFAULT GET_PARAM('GRANULARITY'),
   cascade           BOOLEAN DEFAULT to_cascade_type(GET_PARAM('CASCADE')),
   stattab           VARCHAR2 DEFAULT NULL, 
   statid            VARCHAR2 DEFAULT NULL,
   options           VARCHAR2 DEFAULT 'GATHER AUTO', 
   statown           VARCHAR2 DEFAULT NULL,
   no_invalidate     BOOLEAN DEFAULT
                               to_no_invalidate_type(get_param('NO_INVALIDATE')));

Parameters

Usage Notes

You must have the SYSDBA or both ANALYZE ANY DICTIONARY and ANALYZE ANY system privilege to execute this procedure.

Exceptions

ORA-20000: Index does not exist or insufficient privileges.

ORA-20001: Bad input value.

ORA-20002: Bad user statistics table, may need to upgrade it.

---

GATHER_FIXED_OBJECTS_STATS Procedure

This procedure gathers statistics for all fixed objects (dynamic performance tables).

Syntax

DBMS_STATS.GATHER_FIXED_OBJECTS_STATS (
   stattab        VARCHAR2 DEFAULT NULL,
   statid         VARCHAR2 DEFAULT NULL,
   statown        VARCHAR2 DEFAULT NULL, 
   no_invalidate  BOOLEAN  DEFAULT to_no_invalidate_type (
                                     get_param('NO_INVALIDATE'))); 

Parameters

Usage Notes

You must have the SYSDBA or ANALYZE ANY DICTIONARY system privilege to execute this procedure.

Exceptions

ORA-20000: Insufficient privileges.

ORA-20001: Bad input value.

ORA-20002: Bad user statistics table, may need to upgrade it.

---

GATHER_INDEX_STATS Procedure

This procedure gathers index statistics. It attempts to parallelize as much of the work as possible. Restrictions are described in the individual parameters. This operation will not parallelize with certain types of indexes, including cluster indexes, domain indexes, and bitmap join indexes. The granularity and no_invalidate arguments are not relevant to these types of indexes.

Syntax

DBMS_STATS.GATHER_INDEX_STATS (
   ownname          VARCHAR2, 
   indname          VARCHAR2, 
   partname         VARCHAR2 DEFAULT NULL,
   estimate_percent NUMBER   DEFAULT to_estimate_percent_type 
                                                (GET_PARAM('ESTIMATE_PERCENT')),
   stattab          VARCHAR2 DEFAULT NULL, 
   statid           VARCHAR2 DEFAULT NULL,
   statown          VARCHAR2 DEFAULT NULL,
   degree           NUMBER   DEFAULT to_degree_type(get_param('DEGREE')),
   granularity      VARCHAR2 DEFAULT GET_PARAM('GRANULARITY'),
   no_invalidate    BOOLEAN  DEFAULT to_no_invalidate_type 
                                               (GET_PARAM('NO_INVALIDATE')),
   force            BOOLEAN DEFAULT FALSE);

Parameters

Exceptions

ORA-20000: Index does not exist or insufficient privileges.

ORA-20001: Bad input value.

---

GATHER_SCHEMA_STATS Procedures

This procedure gathers statistics for all objects in a schema.

Syntax

DBMS_STATS.GATHER_SCHEMA_STATS ( 
   ownname          VARCHAR2, 
   estimate_percent NUMBER   DEFAULT to_estimate_percent_type 
                                                (get_param('ESTIMATE_PERCENT')), 
   block_sample     BOOLEAN  DEFAULT FALSE, 
   method_opt       VARCHAR2 DEFAULT get_param('METHOD_OPT'),
   degree           NUMBER   DEFAULT to_degree_type(get_param('DEGREE')), 
   granularity      VARCHAR2 DEFAULT GET_PARAM('GRANULARITY'), 
   cascade          BOOLEAN  DEFAULT to_cascade_type(get_param('CASCADE')), 
   stattab          VARCHAR2 DEFAULT NULL, 
   statid           VARCHAR2 DEFAULT NULL, 
   options          VARCHAR2 DEFAULT 'GATHER', 
   objlist          OUT      ObjectTab,
   statown          VARCHAR2 DEFAULT NULL, 
   no_invalidate    BOOLEAN  DEFAULT to_no_invalidate_type (
                                     get_param('NO_INVALIDATE')),
  force             BOOLEAN DEFAULT FALSE);
   
DBMS_STATS.GATHER_SCHEMA_STATS ( 
   ownname          VARCHAR2, 
   estimate_percent NUMBER   DEFAULT to_estimate_percent_type 
                                                (get_param('ESTIMATE_PERCENT')), 
   block_sample     BOOLEAN  DEFAULT FALSE, 
   method_opt       VARCHAR2 DEFAULT get_param('METHOD_OPT'), 
   degree           NUMBER   DEFAULT to_degree_type(get_param('DEGREE')), 
   granularity      VARCHAR2 DEFAULT GET_PARAM('GRANULARITY'), 
   cascade          BOOLEAN  DEFAULT to_cascade_type(get_param('CASCADE')), 
   stattab          VARCHAR2 DEFAULT NULL, 
   statid           VARCHAR2 DEFAULT NULL, 
   options          VARCHAR2 DEFAULT 'GATHER', 
   statown          VARCHAR2 DEFAULT NULL, 
   no_invalidate    BOOLEAN  DEFAULT to_no_invalidate_type (
                                     get_param('NO_INVALIDATE'), 
   force            BOOLEAN DEFAULT FALSE);

Parameters

Usage Notes

DBMS_STATS.GATHER_SCHEMA_STATS generates differing sampling rates on partitioned tables when you use the auto_sample_size constant. DBMS_STATS tries to determine an adequate sample size for each type of statistic, which is different for each table or column (and each partition, if partitioned). It starts with a sampling rate to get approximately 5000 rows and examines the result based on statistical equations. This process is repeated with increased sampling rate for unsatisfactory results.

In general, the number of distinct values column statistics requires the highest sampling rate among the others, especially when each distinct value repeats a small number of times.

When you use a specific value for the sampling percentage, DBMS_STATS honors it except for when:

• The result is less than 2500 rows (too small a sample) and

• The specified percentage is more than the certain percentage.

Statistics for external tables are not collected by this procedure.

Exceptions

ORA-20000: Schema does not exist or insufficient privileges.

ORA-20001: Bad input value.

---

GATHER_SYSTEM_STATS Procedure

This procedure gathers system statistics.

Syntax

DBMS_STATS.GATHER_SYSTEM_STATS (
   gathering_mode   VARCHAR2 DEFAULT 'NOWORKLOAD',
   interval         INTEGER  DEFAULT NULL,
   stattab          VARCHAR2 DEFAULT NULL,
   statid           VARCHAR2 DEFAULT NULL,
   statown          VARCHAR2 DEFAULT NULL);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid input value.

ORA-20002: Bad user statistics table; may need to be upgraded.

ORA-20003: Unable to gather system statistics.

ORA-20004: Error in the INTERVAL mode: system parameter job_queue_processes must be >0.

---

GATHER_TABLE_STATS Procedure

This procedure gathers table and column (and index) statistics. It attempts to parallelize as much of the work as possible, but there are some restrictions as described in the individual parameters.

Syntax

DBMS_STATS.GATHER_TABLE_STATS (
   ownname          VARCHAR2, 
   tabname          VARCHAR2, 
   partname         VARCHAR2 DEFAULT NULL,
   estimate_percent NUMBER   DEFAULT to_estimate_percent_type 
                                                (get_param('ESTIMATE_PERCENT')), 
   block_sample     BOOLEAN  DEFAULT FALSE,
   method_opt       VARCHAR2 DEFAULT get_param('METHOD_OPT'),
   degree           NUMBER   DEFAULT to_degree_type(get_param('DEGREE')),
   granularity      VARCHAR2 DEFAULT GET_PARAM('GRANULARITY'), 
   cascade          BOOLEAN  DEFAULT to_cascade_type(get_param('CASCADE')),
   stattab          VARCHAR2 DEFAULT NULL, 
   statid           VARCHAR2 DEFAULT NULL,
   statown          VARCHAR2 DEFAULT NULL,
   no_invalidate    BOOLEAN  DEFAULT  to_no_invalidate_type (
                                     get_param('NO_INVALIDATE')),
   force            BOOLEAN DEFAULT FALSE);

Parameters

Usage Notes

This operation does not parallelize if the user does not have select privilege on the table being analyzed.

Exceptions

ORA-20000: Table does not exist or insufficient privileges.

ORA-20001: Bad input value.

---

GENERATE_STATS Procedure

This procedure generates object statistics from previously collected statistics of related objects. The currently supported objects are b-tree and bitmap indexes.

Syntax

DBMS_STATS.GENERATE_STATS (
   ownname   VARCHAR2, 
   objname   VARCHAR2,
   organized NUMBER DEFAULT 7);

Parameters

Usage Notes

For fully populated schemas, the gather procedures should be used instead when more accurate statistics are desired.

Exceptions

ORA-20000: Unsupported object type of object does not exist.

ORA-20001: Invalid option or invalid statistics.

---

GET_COLUMN_STATS Procedures

These procedures gets all column-related information. In the form of this procedure that deals with user-defined statistics, the statistics type returned is the type stored, in addition to the user-defined statistics.

Syntax

DBMS_STATS.GET_COLUMN_STATS (
   ownname     VARCHAR2, 
   tabname     VARCHAR2, 
   colname     VARCHAR2, 
   partname    VARCHAR2 DEFAULT NULL,
   stattab     VARCHAR2 DEFAULT NULL, 
   statid      VARCHAR2 DEFAULT NULL,
   distcnt OUT NUMBER, 
   density OUT NUMBER,
   nullcnt OUT NUMBER, 
   srec    OUT StatRec,
   avgclen OUT NUMBER,
   statown     VARCHAR2 DEFAULT NULL);

Use the following for user-defined statistics:

DBMS_STATS.GET_COLUMN_STATS (
   ownname          VARCHAR2, 
   tabname          VARCHAR2, 
   colname          VARCHAR2, 
   partname         VARCHAR2 DEFAULT NULL,
   stattab          VARCHAR2 DEFAULT NULL, 
   statid           VARCHAR2 DEFAULT NULL,
   ext_stats   OUT  RAW,
   stattypown  OUT  VARCHAR2 DEFAULT NULL, 
   stattypname OUT  VARCHAR2 DEFAULT NULL, 
   statown          VARCHAR2 DEFAULT NULL);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges or no statistics have been stored for requested object.

---

GET_INDEX_STATS Procedures

These procedures get all index-related information. In the form of this procedure that deals with user-defined statistics, the statistics type returned is the type stored, in addition to the user-defined statistics.

Syntax

DBMS_STATS.GET_INDEX_STATS (
   ownname        VARCHAR2, 
   indname        VARCHAR2,
   partname       VARCHAR2 DEFAULT NULL,
   stattab        VARCHAR2 DEFAULT NULL, 
   statid         VARCHAR2 DEFAULT NULL,
   numrows    OUT NUMBER, 
   numlblks   OUT NUMBER,
   numdist    OUT NUMBER, 
   avglblk    OUT NUMBER,
   avgdblk    OUT NUMBER, 
   clstfct    OUT NUMBER,
   indlevel   OUT NUMBER,
   statown        VARCHAR2 DEFAULT NULL,
   cachedblk  OUT NUMBER,
   cachehit   OUT NUMBER);

DBMS_STATS.GET_INDEX_STATS (
   ownname        VARCHAR2, 
   indname        VARCHAR2,
   partname       VARCHAR2 DEFAULT NULL,
   stattab        VARCHAR2 DEFAULT NULL, 
   statid         VARCHAR2 DEFAULT NULL,
   numrows    OUT NUMBER, 
   numlblks   OUT NUMBER,
   numdist    OUT NUMBER, 
   avglblk    OUT NUMBER,
   avgdblk    OUT NUMBER, 
   clstfct    OUT NUMBER,
   indlevel   OUT NUMBER,
   statown        VARCHAR2 DEFAULT NULL,
   guessq     OUT NUMBER,
   cachedblk  OUT NUMBER,
   cachehit   OUT NUMBER);

Use the following for user-defined statistics:

DBMS_STATS.GET_INDEX_STATS (
   ownname          VARCHAR2, 
   indname          VARCHAR2,
   partname         VARCHAR2 DEFAULT NULL,
   stattab          VARCHAR2 DEFAULT NULL, 
   statid           VARCHAR2 DEFAULT NULL,
   ext_stats   OUT  RAW,
   stattypown  OUT  VARCHAR2 DEFAULT NULL, 
   stattypname OUT  VARCHAR2 DEFAULT NULL, 
   statown          VARCHAR2 DEFAULT NULL,
   cachedblk        OUT NUMBER,
   cachehit         OUT NUMBER);

Parameters

Usage Notes

• The Optimizer uses the cached data to estimate number of cached blocks for index or statistics table access. The total cost of the operation will be combined from the I/O cost of reading not cached blocks from disk, the CPU cost of getting cached blocks from the buffer cache, and the CPU cost of processing the data.

• Oracle maintains cachedblk and cachehit at all times but uses correspondent caching statistics for optimization as part of the table and index statistics only when the user calls DBMS_STATS.GATHER_[TABLE/INDEX/SCHEMA/DATABASE]_STATS procedure for auto mode or DBMS_STATS.GATHER_SYSTEM_STATS for manual mode. In order to prevent the user from utilizing inaccurate and unreliable data, the optimizer will compute a 'confidence factor' for each cachehit and a cachedblk for each object. If the 'confidence factor' for the value meets confidence criteria, this value will be used, otherwise the defaults will be used.

• The automatic maintenance algorithm for object caching statistics assumes that there is only one major workload for the system and adjusts statistics to this workload, ignoring other "minor" workloads. If this is not the case, you must use manual mode for maintaining object caching statistics.

• The object caching statistics maintenance algorithm for auto mode prevents you from using statistics in the following situations

  • When not enough data has been analyzed, such as when an object has been recently create

  • When the system does not have one major workload resulting in averages not corresponding to real values.

Exceptions

ORA-20000: Object does not exist or insufficient privileges or no statistics have been stored for requested object.

---

GET_PARAM Function

This function returns the default value of parameters of DBMS_STATS procedures.

Syntax

DBMS_STATS.GET_PARAM (
   pname     IN   VARCHAR2)
 RETURN VARCHAR2;

Parameters

Exceptions

ORA-20001: Invalid input values

---

GET_STATS_HISTORY_AVAILABILITY Function

This function returns oldest timestamp where statistics history is available.Users cannot restore statistics to a timestamp older than this one.

Syntax

DBMS_STATS.GET_STATS_HISTORY_AVAILABILITY
 RETURN TIMESTAMP WITH TIMEZONE;

---

GET_STATS_HISTORY_RETENTION Function

This function returns the current retention value.

Syntax

DBMS_STATS.GET_STATS_HISTORY_RETENTION
 RETURN NUMBER;

---

GET_SYSTEM_STATS Procedure

This procedure gets system statistics from stattab, or from the dictionary if stattab is NULL.

Syntax

DBMS_STATS.GET_SYSTEM_STATS (
   status    OUT  VARCHAR2,
   dstart    OUT  DATE,
   dstop     OUT  DATE,
   pname          VARCHAR2,
   pvalue    OUT  NUMBER,
   stattab   IN   VARCHAR2 DEFAULT NULL, 
   statid    IN   VARCHAR2 DEFAULT NULL,
   statown   IN   VARCHAR2 DEFAULT NULL);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20002: Bad user statistics table; may need to be upgraded.

ORA-20003: Unable to gather system statistics.

ORA-20004: Parameter does not exist.

---

GET_TABLE_STATS Procedure

This procedure gets all table-related information.

Syntax

DBMS_STATS.GET_TABLE_STATS (
   ownname         VARCHAR2, 
   tabname         VARCHAR2, 
   partname        VARCHAR2 DEFAULT NULL,
   stattab         VARCHAR2 DEFAULT NULL,
   statid          VARCHAR2 DEFAULT NULL,
   numrows     OUT NUMBER, 
   numblks     OUT NUMBER,
   avgrlen     OUT NUMBER,
   statown         VARCHAR2 DEFAULT NULL,
   cachedblk   OUT NUMBER,
   cachehit    OUT NUMBER);

Parameters

Usage Notes

• The Optimizer uses the cached data to estimate number of cached blocks for index or statistics table access. The total cost of the operation will be combined from the I/O cost of reading not cached blocks from disk, the CPU cost of getting cached blocks from the buffer cache, and the CPU cost of processing the data.

• Oracle maintains cachedblk and cachehit at all times but uses correspondent caching statistics for optimization as part of the table and index statistics only when the user calls DBMS_STATS.GATHER_[TABLE/INDEX/SCHEMA/DATABASE]_STATS procedure for auto mode or DBMS_STATS.GATHER_SYSTEM_STATS for manual mode. In order to prevent the user from utilizing inaccurate and unreliable data, the optimizer will compute a 'confidence factor' for each cachehit and a cachedblk for each object. If the 'confidence factor' for the value meets confidence criteria, this value will be used, otherwise the defaults will be used.

• The automatic maintenance algorithm for object caching statistics assumes that there is only one major workload for the system and adjusts statistics to this workload, ignoring other "minor" workloads. If this is not the case, you must use manual mode for maintaining object caching statistics.

• The object caching statistics maintenance algorithm for auto mode prevents you from using statistics in the following situations

  • When not enough data has been analyzed, such as when an object has been recently create

  • When the system does not have one major workload resulting in averages not corresponding to real values.

Exceptions

ORA-20000: Object does not exist or insufficient privileges or no statistics have been stored for requested object

---

IMPORT_COLUMN_STATS Procedure

This procedure retrieves statistics for a particular column from the user statistics table identified by stattab and stores them in the dictionary.

Syntax

DBMS_STATS.IMPORT_COLUMN_STATS (
   ownname       VARCHAR2, 
   tabname       VARCHAR2, 
   colname       VARCHAR2,
   partname      VARCHAR2 DEFAULT NULL,
   stattab       VARCHAR2, 
   statid        VARCHAR2 DEFAULT NULL,
   statown       VARCHAR2 DEFAULT NULL,
   no_invalidate BOOLEAN DEFAULT to_no_invalidate_type (
                                     get_param('NO_INVALIDATE')),
   force         BOOLEAN DEFAULT FALSE);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid or inconsistent values in the user statistics table.

ORA-20005: Object statistics are locked.

---

IMPORT_DATABASE_STATS Procedure

This procedure retrieves statistics for all objects in the database from the user statistics table(s) and stores them in the dictionary.

Syntax

DBMS_STATS.IMPORT_DATABASE_STATS (
   stattab       VARCHAR2, 
   statid        VARCHAR2 DEFAULT NULL,
   statown       VARCHAR2 DEFAULT NULL,
   no_invalidate BOOLEAN DEFAULT to_no_invalidate_type(
                                    get_param('NO_INVALIDATE')),
   force         BOOLEAN DEFAULT FALSE);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid or inconsistent values in the user statistics table.

---

IMPORT_DICTIONARY_STATS Procedure

This procedure retrieves statistics for all dictionary schemas ('SYS', 'SYSTEM' and RDBMS component schemas) from the user statistics table and stores them in the dictionary.

Syntax

DBMS_STATS.IMPORT_DICTIONARY_STATS (
   stattab       VARCHAR2, 
   statid        VARCHAR2 DEFAULT NULL,
   statown       VARCHAR2 DEFAULT NULL,
   no_invalidate BOOLEAN DEFAULT to_no_invalidate_type(
                                    get_param('NO_INVALIDATE')),
   force         BOOLEAN DEFAULT FALSE);

Parameters

Usage Notes

You must have the SYSDBA or both ANALYZE ANY DICTIONARY and ANALYZE ANY system privilege to execute this procedure.

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid or inconsistent values in the user statistics table.

ORA-20002: Bad user statistics table, may need to upgrade it.

---

IMPORT_FIXED_OBJECTS_STATS Procedure

This procedure retrieves statistics for fixed tables from the user statistics table(s) and stores them in the dictionary.

Syntax

DBMS_STATS.IMPORT_FIXED_OBJECTS_STATS (
   stattab       VARCHAR2, 
   statid        VARCHAR2 DEFAULT NULL,
   statown       VARCHAR2 DEFAULT NULL,
   no_invalidate BOOLEAN DEFAULT to_no_invalidate_type(
                                    get_param('NO_INVALIDATE')),
   force         BOOLEAN DEFAULT FALSE);

Parameters

Usage Notes

You must have the SYSDBA or ANALYZE ANY DICTIONARY system privilege to execute this procedure.

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid or inconsistent values in the user statistics table.

ORA-20002: Bad user statistics table, may need to upgrade it.

---

IMPORT_INDEX_STATS Procedure

http://usunnab06.us.oracle.com:80/servers/MifChecker/Out/Y10312_01.htm retrieves statistics for a particular index from the user statistics table identified by stattab and stores them in the dictionary.

Syntax

DBMS_STATS.IMPORT_INDEX_STATS (
   ownname       VARCHAR2, 
   indname       VARCHAR2,
   partname      VARCHAR2 DEFAULT NULL,
   stattab       VARCHAR2, 
   statid        VARCHAR2 DEFAULT NULL,
   statown       VARCHAR2 DEFAULT NULL,
   no_invalidate BOOLEAN DEFAULT to_no_invalidate_type(
                                    get_param('NO_INVALIDATE')),
   force         BOOLEAN DEFAULT FALSE);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid or inconsistent values in the user statistics table.

ORA-20005: Object statistics are locked.

---

IMPORT_SCHEMA_STATS Procedure

http://usunnab06.us.oracle.com:80/servers/MifChecker/Out/Y10312_01.htm retrieves statistics for all objects in the schema identified by ownname from the user statistics table and stores them in the dictionary.

Syntax

DBMS_STATS.IMPORT_SCHEMA_STATS (
   ownname       VARCHAR2,
   stattab       VARCHAR2, 
   statid        VARCHAR2 DEFAULT NULL,
   statown       VARCHAR2 DEFAULT NULL,
   no_invalidate BOOLEAN DEFAULTto_no_invalidate_type(
                                    get_param('NO_INVALIDATE')),
   force         BOOLEAN DEFAULT FALSE);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid or inconsistent values in the user statistics table.

---

IMPORT_SYSTEM_STATS Procedure

http://usunnab06.us.oracle.com:80/servers/MifChecker/Out/Y10312_01.htm retrieves system statistics from the user statistics table, identified by stattab, and stores the statistics in the dictionary.

Syntax

DBMS_STATS.IMPORT_SYSTEM_STATS (
   stattab       VARCHAR2, 
   statid        VARCHAR2 DEFAULT NULL,
   statown       VARCHAR2 DEFAULT NULL);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid or inconsistent values in the user statistics table.

ORA-20002: Bad user statistics table; may need to be upgraded.

ORA-20003: Unable to import system statistics.

---

IMPORT_TABLE_STATS Procedure

http://usunnab06.us.oracle.com:80/servers/MifChecker/Out/Y10312_01.htm retrieves statistics for a particular table from the user statistics table identified by stattab and stores them in the dictionary. Cascade results in all index and column statistics associated with the specified table being imported as well.

Syntax

DBMS_STATS.IMPORT_TABLE_STATS (
   ownname       VARCHAR2, 
   tabname       VARCHAR2,
   partname      VARCHAR2 DEFAULT NULL,
   stattab       VARCHAR2, 
   statid        VARCHAR2 DEFAULT NULL,
   cascade       BOOLEAN  DEFAULT TRUE,
   statown       VARCHAR2 DEFAULT NULL,
   no_invalidate BOOLEAN DEFAULT to_no_invalidate_type(
                                    get_param('NO_INVALIDATE')),
   force         BOOLEAN DEFAULT FALSE);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid or inconsistent values in the user statistics table.

---

LOCK_SCHEMA_STATS Procedure

This procedure locks the statistics of all tables of a schema.

Syntax

DBMS_STATS.LOCK_SCHEMA_STATS (
   ownname    VARCHAR2);

Parameters

Usage Notes

See "Usage Notes" for LOCK_TABLE_STATS Procedure.

---

LOCK_TABLE_STATS Procedure

This procedure locks the statistics on the table.

Syntax

DBMS_STATS.LOCK_TABLE_STATS (
   ownname    VARCHAR2,
   tabname    VARCHAR2);

Parameters

Usage Notes

• When statistics on a table are locked, all the statistics depending on the table, including table statistics, column statistics, histograms and statistics on all dependent indexes, are considered to be locked.

• The SET_*, DELETE_*, IMPORT_*, GATHER_* procedures that modify statistics in the dictionary of an individual table, index or column will raise an error if statistics of the object is locked.

• Procedures that operates on multiple objects (such as GATHER_SCHEMA_STATS) will skip modifying the statistics of an object if it is locked. Many procedures have force argument to override the lock.

• This procedure either freezes the current set of the statistics or keeps the statistics empty (uncollected) to use Dynamic Sampling.

• The locked or unlocked state is not exported along with the table statistics when using EXPORT_*_STATS procedures.

---

PREPARE_COLUMN_VALUES Procedures

These procedures convert user-specified minimum, maximum, and histogram endpoint datatype-specific values into Oracle's internal representation for future storage using SET_COLUMN_STATS.

Syntax

DBMS_STATS.PREPARE_COLUMN_VALUES (
   srec     IN OUT StatRec, 
   charvals        CHARARRAY);

DBMS_STATS.PREPARE_COLUMN_VALUES (
   srec      IN OUT StatRec, 
   datevals         DATEARRAY);

DBMS_STATS.PREPARE_COLUMN_VALUES ( 
   srec     IN OUT StatRec, 
   dblvals         DBLARRAY);

DBMS_STATS.PREPARE_COLUMN_VALUES ( 
   srec     IN OUT StatRec, 
   fltvals         FLTARRAY);

DBMS_STATS.PREPARE_COLUMN_VALUES (
   srec     IN OUT StatRec, 
   numvals         NUMARRAY);

DBMS_STATS.PREPARE_COLUMN_VALUES ( 
   srec     IN OUT StatRec, 
   rawvals         RAWARRAY);

Pragmas

pragma restrict_references(prepare_column_values, WNDS, RNDS, WNPS, RNPS);
pragma restrict_references(prepare_column_values_nvarchar, WNDS, RNDS, WNPS, RNPS);
pragma restrict_references(prepare_column_values_rowid, WNDS, RNDS, WNPS, RNPS);

Parameters

Datatype-specific input parameters (use one) are shown in Table 103-50.

Output Parameters

Exceptions

ORA-20001: Invalid or inconsistent input values.

---

PREPARE_COLUMN_VALUES_NVARCHAR2 Procedure

This procedure converts user-specified minimum, maximum, and histogram endpoint datatype-specific values into Oracle's internal representation for future storage using SET_COLUMN_STATS.

Syntax

DBMS_STATS.PREPARE_COLUMN_VALUES_NVARCHAR2 (
   srec     IN OUT StatRec, 
   nvmin           NVARCHAR2, 
   nvmax           NVARCHAR2);

Pragmas

pragma restrict_references(prepare_column_values_nvarchar, WNDS, RNDS, WNPS, RNPS);

Parameters

Datatype-specific input parameters (use one) are shown in Table 103-50.

Output Parameters

Exceptions

ORA-20001: Invalid or inconsistent input values.

---

PREPARE_COLUMN_VALUES_ROWID Procedure

This procedure converts user-specified minimum, maximum, and histogram endpoint datatype-specific values into Oracle's internal representation for future storage using SET_COLUMN_STATS.

Syntax

DBMS_STATS.PREPARE_COLUMN_VALUES_ROWID (
   srec  IN OUT StatRec, 
   rwmin        ROWID, 
   rwmax        ROWID);

Pragmas

pragma restrict_references(prepare_column_values_rowid, WNDS, RNDS, WNPS, RNPS);

Parameters

Datatype-specific input parameters (use one) are shown in Table 103-50.

Output Parameters

Exceptions

ORA-20001: Invalid or inconsistent input values.

---

PURGE_STATS Procedure

This procedure purges old versions of statistics saved in the dictionary. To run this procedure, you must have the SYSDBA or both ANALYZE ANY DICTIONARY and ANALYZE ANY system privilege.

Syntax

DBMS_STATS.PURGE_STATS( 
    before_timestamp       TIMESTAMP WITH TIME ZONE);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid or inconsistent values.

---

RESET_PARAM_DEFAULTS Procedure

This procedure resets the default values of all parameters to Oracle recommended values.

Syntax

DBMS_STATS.RESET_PARAM_DEFAULTS;

---

RESTORE_DATABASE_STATS Procedure

This procedure restores statistics of all tables of the database as of a specified timestamp (as_of_timestamp).

Syntax

DBMS_STATS.RESTORE_DATABSE_STATS( 
   as_of_timestamp        TIMESTAMP WITH TIME ZONE, 
   force                  BOOLEAN DEFAULT FALSE,
   no_invalidate          BOOLEAN DEFAULT to_no_invalidate_type
                                                    (GET_PARAM('NO_INVALIDATE')));

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid or inconsistent values.

ORA-20006: Unable to restore statistics, statistics history not available.

---

RESTORE_DICTIONARY_STATS Procedure

This procedure restores statistics of all dictionary tables (tables of 'SYS', 'SYSTEM' and RDBMS component schemas) as of a specified timestamp (as_of_timestamp).

Syntax

DBMS_STATS.RESTORE_DICTIONARY_STATS( 
   as_of_timestamp        TIMESTAMP WITH TIME ZONE, 
   force                  BOOLEAN DEFAULT FALSE,
   no_invalidate          BOOLEAN DEFAULT to_no_invalidate_type
                                                    (GET_PARAM('NO_INVALIDATE')));

Parameters

Usage Notes

To run this procedure, you must have the SYSDBA or both ANALYZE ANY DICTIONARY and ANALYZE ANY system privilege.

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid or inconsistent values.

ORA-20006: Unable to restore statistics, statistics history not available.

---

RESTORE_FIXED_OBJECTS_STATS Procedure

This procedure restores statistics of all fixed tables as of a specified timestamp (as_of_timestamp).

Syntax

DBMS_STATS.RESTORE_FIXED_OBJECTS_STATS( 
   as_of_timestamp        TIMESTAMP WITH TIME ZONE, 
   force                  BOOLEAN DEFAULT FALSE,
   no_invalidate          BOOLEAN DEFAULT to_no_invalidate_type
                                                    (GET_PARAM('NO_INVALIDATE')));

Parameters

Usage Notes

To run this procedure, you must have the SYSDBA or ANALYZE ANY DICTIONARY system privilege.

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid or inconsistent values.

ORA-20006: Unable to restore statistics, statistics history not available.

---

RESTORE_SCHEMA_STATS Procedure

This procedure restores statistics of all tables of a schema as of a specified timestamp (as_of_timestamp).

Syntax

DBMS_STATS.RESTORE_SCHEMA_STATS( 
   ownname                VARCHAR2, 
   as_of_timestamp        TIMESTAMP WITH TIME ZONE, 
   force                  BOOLEAN DEFAULT FALSE,
   no_invalidate          BOOLEAN DEFAULT to_no_invalidate_type
                                                    (GET_PARAM('NO_INVALIDATE')));

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid or inconsistent values.

ORA-20006: Unable to restore statistics, statistics history not available.

---

RESTORE_SYSTEM_STATS Procedure

This procedure restores system statistics as of a specified timestamp (as_of_timestamp).

Syntax

DBMS_STATS.RESTORE_SCHEMA_STATS( 
   as_of_timestamp        TIMESTAMP WITH TIME ZONE);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid or inconsistent values.

ORA-20006: Unable to restore statistics, statistics history not available.

---

RESTORE_TABLE_STATS Procedure

This procedure restores statistics of a table as of a specified timestamp (as_of_timestamp). The procedure will restore statistics of associated indexes and columns as well. If the table statistics were locked at the specified timestamp the procedure will lock the statistics. The procedure will not restore user defined statistics.

Syntax

DBMS_STATS.RESTORE_TABLE_STATS (
   ownname                   VARCHAR2, 
   tabname                   VARCHAR2, 
   as_of_timestamp           TIMESTAMP WITH TIME ZONE,
   restore_cluster_index     BOOLEAN DEFAULT FALSE,
   force                     BOOLEAN DEFAULT FALSE,
   no_invalidate             BOOLEAN DEFAULT to_no_invalidate_type
                                                    (GET_PARAM('NO_INVALIDATE')));

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid or inconsistent values.

ORA-20006: Unable to restore statistics, statistics history not available.

---

SET_COLUMN_STATS Procedures

This procedure sets column-related information. In the version of this procedure that deals with user-defined statistics, the statistics type specified is the type to store in the dictionary, in addition to the actual user-defined statistics. If this statistics type is NULL, the statistics type associated with the index or column is stored.

Syntax

DBMS_STATS.SET_COLUMN_STATS (
   ownname       VARCHAR2, 
   tabname       VARCHAR2, 
   colname       VARCHAR2, 
   partname      VARCHAR2 DEFAULT NULL,
   stattab       VARCHAR2 DEFAULT NULL, 
   statid        VARCHAR2 DEFAULT NULL,
   distcnt       NUMBER DEFAULT NULL,
   density       NUMBER DEFAULT NULL,
   nullcnt       NUMBER DEFAULT NULL,
   srec          StatRec DEFAULT NULL,
   avgclen       NUMBER DEFAULT NULL,
   flags         NUMBER DEFAULT NULL,
   statown       VARCHAR2 DEFAULT NULL,
   no_invalidate BOOLEAN DEFAULT to_no_invalidate_type(
                                    get_param('NO_INVALIDATE')),
   force         BOOLEAN DEFAULT FALSE);

Use the following for user-defined statistics:

DBMS_STATS.SET_COLUMN_STATS (
   ownname       VARCHAR2, 
   tabname       VARCHAR2, 
   colname       VARCHAR2, 
   partname      VARCHAR2 DEFAULT NULL,
   stattab       VARCHAR2 DEFAULT NULL, 
   statid        VARCHAR2 DEFAULT NULL,
   ext_stats     RAW,
   stattypown    VARCHAR2 DEFAULT NULL, 
   stattypname   VARCHAR2 DEFAULT NULL, 
   statown       VARCHAR2 DEFAULT NULL,
   no_invalidate BOOLEAN DEFAULT to_no_invalidate_type(
                                    get_param('NO_INVALIDATE')),
   force         BOOLEAN DEFAULT FALSE);

Parameters

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid or inconsistent input values.

ORA-20005: Object statistics are locked.

---

SET_INDEX_STATS Procedures

These procedures set index-related information. In the version of this procedure that deals with user-defined statistics, the statistics type specified is the type to store in the dictionary, in addition to the actual user-defined statistics. If this statistics type is NULL, the statistics type associated with the index or column is stored.

Syntax

DBMS_STATS.SET_INDEX_STATS (
   ownname       VARCHAR2, 
   indname       VARCHAR2,
   partname      VARCHAR2  DEFAULT NULL,
   stattab       VARCHAR2  DEFAULT NULL, 
   statid        VARCHAR2  DEFAULT NULL,
   numrows       NUMBER    DEFAULT NULL, 
   numlblks      NUMBER    DEFAULT NULL,
   numdist       NUMBER    DEFAULT NULL, 
   avglblk       NUMBER    DEFAULT NULL,
   avgdblk       NUMBER    DEFAULT NULL, 
   clstfct       NUMBER    DEFAULT NULL,
   indlevel      NUMBER    DEFAULT NULL, 
   flags         NUMBER    DEFAULT NULL,
   statown       VARCHAR2  DEFAULT NULL,
   no_invalidate BOOLEAN   DEFAULT to_no_invalidate_type(
                                    get_param('NO_INVALIDATE')),
   guessq        NUMBER    DEFAULT NULL,
   cachedblk     NUMBER    DEFAULT NULL,
   cachehit      NUMBER    DEFUALT NULL,
   force         BOOLEAN   DEFAULT FALSE);

Use the following for user-defined statistics:

DBMS_STATS.SET_INDEX_STATS (
   ownname       VARCHAR2, 
   indname       VARCHAR2,
   partname      VARCHAR2  DEFAULT NULL,
   stattab       VARCHAR2  DEFAULT NULL, 
   statid        VARCHAR2  DEFAULT NULL,
   ext_stats     RAW,
   stattypown    VARCHAR2 DEFAULT NULL, 
   stattypname   VARCHAR2 DEFAULT NULL, 
   statown       VARCHAR2 DEFAULT NULL,
   no_invalidate BOOLEAN DEFAULT to_no_invalidate_type(
                                    get_param('NO_INVALIDATE')),
   cachedblk     NUMBER    DEFAULT NULL,
   cachehit      NUMBER    DEFUALT NULL,
   force         BOOLEAN   DEFAULT FALSE);

Parameters

Usage Notes

• The Optimizer uses the cached data to estimate number of cached blocks for index or statistics table access. The total cost of the operation will be combined from the I/O cost of reading not cached blocks from disk, the CPU cost of getting cached blocks from the buffer cache, and the CPU cost of processing the data.

• Oracle maintains cachedblk and cachehit at all times but uses correspondent caching statistics for optimization as part of the table and index statistics only when the user calls DBMS_STATS.GATHER_[TABLE/INDEX/SCHEMA/DATABASE]_STATS procedure for auto mode or DBMS_STATS.GATHER_SYSTEM_STATS for manual mode. In order to prevent the user from utilizing inaccurate and unreliable data, the optimizer will compute a 'confidence factor' for each cachehit and a cachedblk for each object. If the 'confidence factor' for the value meets confidence criteria, this value will be used, otherwise the defaults will be used.

• The automatic maintenance algorithm for object caching statistics assumes that there is only one major workload for the system and adjusts statistics to this workload, ignoring other "minor" workloads. If this is not the case, you must use manual mode for maintaining object caching statistics.

• The object caching statistics maintenance algorithm for auto mode prevents you from using statistics in the following situations

  • When not enough data has been analyzed, such as when an object has been recently create

  • When the system does not have one major workload resulting in averages not corresponding to real values.

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid input value.

ORA-20005: Object statistics are locked.

---

SET_PARAM Procedure

This procedure sets default values for parameters of DBMS_STATS procedures. You can use the GET_PARAM Function to get the current default value of a parameter.

Syntax

DBMS_STATS.SET_PARAM (
   pname      IN    VARCHAR2, 
   pval       IN    VARCHAR2);

Parameters

Usage Notes

• To run this procedure, you must have the SYSDBA or both the ANALYZE ANY DICTIONARY and ANALYZE ANY system privileges.

• Note that both arguments are of type VARCHAR2 and the values need to be enclosed in quotes.

• Note also the difference between NULL and 'NULL':

  • When NULL is unquoted, this sets the parameter to the value Oracle recommends.

  • In the case of the quoted 'NULL', this sets the value of the parameter to NULL.

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid or illegal input value.

Examples

DBMS_STATS.SET_PARAM('CASCADE','DBMS_STATS.AUTO_CASCADE');
DBMS_STATS.SET_PARAM('ESTIMATE_PERCENT','5');
DBMS_STATS.SET_PARAM('DEGREE','NULL');

---

SET_SYSTEM_STATS Procedure

This procedure sets systems statistics.

Syntax

DBMS_STATS.SET_SYSTEM_STATS (
   pname          VARCHAR2,
   pvalue         NUMBER,
   stattab   IN   VARCHAR2 DEFAULT NULL, 
   statid    IN   VARCHAR2 DEFAULT NULL,
   statown   IN   VARCHAR2 DEFAULT NULL);

Parameters

Usage Notes

• The Optimizer uses the cached data to estimate number of cached blocks for index or statistics table access. The total cost of the operation will be combined from the I/O cost of reading not cached blocks from disk, the CPU cost of getting cached blocks from the buffer cache, and the CPU cost of processing the data.

• Oracle maintains cachedblk and cachehit at all times but uses correspondent caching statistics for optimization as part of the table and index statistics only when the user calls DBMS_STATS.GATHER_[TABLE/INDEX/SCHEMA/DATABASE]_STATS procedure for auto mode or DBMS_STATS.GATHER_SYSTEM_STATS for manual mode. In order to prevent the user from utilizing inaccurate and unreliable data, the optimizer will compute a 'confidence factor' for each cachehit and a cachedblk for each object. If the 'confidence factor' for the value meets confidence criteria, this value will be used, otherwise the defaults will be used.

• The automatic maintenance algorithm for object caching statistics assumes that there is only one major workload for the system and adjusts statistics to this workload, ignoring other "minor" workloads. If this is not the case, you must use manual mode for maintaining object caching statistics.

• The object caching statistics maintenance algorithm for auto mode prevents you from using statistics in the following situations

  • When not enough data has been analyzed, such as when an object has been recently create

  • When the system does not have one major workload resulting in averages not corresponding to real values.

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid input value.

ORA-20002: Bad user statistics table; may need to be upgraded.

ORA-20003: Unable to set system statistics.

ORA-20004: Parameter does not exist.

---

SET_TABLE_STATS Procedure

This procedure sets table-related information.

Syntax

DBMS_STATS.SET_TABLE_STATS (
   ownname       VARCHAR2, 
   tabname       VARCHAR2, 
   partname      VARCHAR2 DEFAULT NULL,
   stattab       VARCHAR2 DEFAULT NULL, 
   statid        VARCHAR2 DEFAULT NULL,
   numrows       NUMBER   DEFAULT NULL, 
   numblks       NUMBER   DEFAULT NULL,
   avgrlen       NUMBER   DEFAULT NULL, 
   flags         NUMBER   DEFAULT NULL,
   statown       VARCHAR2 DEFAULT NULL,
   no_invalidate BOOLEAN  DEFAULT to_no_invalidate_type (
                                     get_param('NO_INVALIDATE')),
   cachedblk     NUMBER    DEFAULT NULL,
   cachehit      NUMBER    DEFUALT NULL,
   force         BOOLEAN   DEFAULT FALSE);

Parameters

Usage Notes

• The Optimizer uses the cached data to estimate number of cached blocks for index or statistics table access. The total cost of the operation will be combined from the I/O cost of reading not cached blocks from disk, the CPU cost of getting cached blocks from the buffer cache, and the CPU cost of processing the data.

• Oracle maintains cachedblk and cachehit at all times but uses correspondent caching statistics for optimization as part of the table and index statistics only when the user calls DBMS_STATS.GATHER_[TABLE/INDEX/SCHEMA/DATABASE]_STATS procedure for auto mode or DBMS_STATS.GATHER_SYSTEM_STATS for manual mode. In order to prevent the user from utilizing inaccurate and unreliable data, the optimizer will compute a 'confidence factor' for each cachehit and a cachedblk for each object. If the 'confidence factor' for the value meets confidence criteria, this value will be used, otherwise the defaults will be used.

• The automatic maintenance algorithm for object caching statistics assumes that there is only one major workload for the system and adjusts statistics to this workload, ignoring other "minor" workloads. If this is not the case, you must use manual mode for maintaining object caching statistics.

• The object caching statistics maintenance algorithm for auto mode prevents you from using statistics in the following situations

  • When not enough data has been analyzed, such as when an object has been recently create

  • When the system does not have one major workload resulting in averages not corresponding to real values.

Exceptions

ORA-20000: Object does not exist or insufficient privileges.

ORA-20001: Invalid input value.

ORA-20005: Object statistics are locked.

---

UNLOCK_SCHEMA_STATS Procedure

This procedure unlocks the statistics on all the tables in schema.

Syntax

DBMS_STATS.UNLOCK_SCHEMA_STATS (
   ownname    VARCHAR2);

Parameters

Usage Notes

• When statistics on a table is locked, all the statistics depending on the table, including table statistics, column statistics, histograms and statistics on all dependent indexes, are considered to be locked.

• The SET_*, DELETE_*, IMPORT_*, GATHER_* procedures that modify statistics in the dictionary of an individual table, index or column will raise an error if statistics of the object is locked.

• Procedures that operates on multiple objects (such as GATHER_SCHEMA_STATS) will skip modifying the statistics of an object if it is locked. Many procedures have force argument to override the lock.

---

UNLOCK_TABLE_STATS Procedure

This procedure unlocks the statistics on the table.

Syntax

DBMS_STATS.UNLOCK_TABLE_STATS (
   ownname    VARCHAR2,
   tabname    VARCHAR2);

Parameters

Usage Notes

• When statistics on a table is locked, all the statistics depending on the table, including table statistics, column statistics, histograms and statistics on all dependent indexes, are considered to be locked.

• The SET_*, DELETE_*, IMPORT_*, GATHER_* procedures that modify statistics in the dictionary of an individual table, index or column will raise an error if statistics of the object is locked.

• Procedures that operates on multiple objects (such as GATHER_SCHEMA_STATS) will skip modifying the statistics of an object if it is locked. Many procedures have force argument to override the lock.

---

UPGRADE_STAT_TABLE Procedure

This procedure upgrades a user statistics table from an older version.

Syntax

DBMS_STATS.UPGRADE_STAT_TABLE (
   ownname    VARCHAR2,
   stattab    VARCHAR2);

Parameters

Exceptions

ORA-20000: Unable to upgrade table.