C Optimal Flexible Architecture

C.1.1 Characteristics of an Optimal Flexible Architecture-Compliant Installation

An Optimal Flexible Architecture-compliant database has the following characteristics:

• Independent subdirectories

  Categories of files are separated into independent subdirectories so that files in one category are minimally affected by operations on files in other categories.

• Consistent naming conventions for database files

  Database files are easily distinguishable from all other files. Files of one database are easily distinguishable from files of another database. Data files, redo log files, and control files are easily identifiable. Data f iles are clearly associated with a particular tablespace.

• Integrity of Oracle home directories

  You can add, move, or delete Oracle home directories without having to revise applications that refer to them.

• Separation of administrative information for each database

  The ability to distinguish administrative information about one database from that of another ensures a reasonable structure for the organization and storage of administrative data.

• Separation of tablespace contents

  Tablespace free space fragmentation and I/O request contention are minimized, while administrative flexibility is maximized.

• Tuning I/O loads across all disks

  I/O loads are tuned across all disks, including disks storing Oracle data in raw devices, if needed.

C.3.1 Top-Level Oracle Directory

In an Oracle8i release 8.1.3 or earlier release, all subdirectories are located under a top-level ORACLE_HOME directory that by default is c:\orant.

When you install an Oracle8i release 8.1.4 or later Optimal Flexible Architecture-compliant database, all subdirectories are no longer under a top-level ORACLE_HOME directory. There is now a new top-level Oracle base directory of the form DRIVE_LETTER:\oracle\product\10.2.0, where DRIVE_LETTER is any hard drive.

The Oracle base directory contains \ORACLE_HOME directories, \oradata directories (for database files), \flash_recovery_area (for recovery operations), and \admin directories (for database administration files).

C.3.2 Database File Names

In Oracle8i release 8.1.3 and earlier releases, database files have the SID in the database file name. For example, the first control file is named ctl1SID.ora.

Beginning with Oracle8i release 8.1.4, database files no longer have the SID in the database file name. For example, the first control file is named control01.ctl. There is no need for the presence of the SID in the file name, because all the database files for a particular database are placed in \oradata under a directory called DB_NAME that is named for that database.

C.3.3 Database File Name Extensions

In Oracle8i release 8.1.3 and earlier releases, all database files have the same .ORA extension.

In an Optimal Flexible Architecture-compliant release, the convention of having .ora as the filename extension for database files is no longer used. Database filenames now have more meaningful extensions. These are:

• .ctl for control files

• .log for log files

• .dbf for data files

C.4.1 ORACLE_BASE Directory

ORACLE_BASE is the root of the Oracle directory tree. If you install an Optimal Flexible Architecture-compliant database using Oracle Universal Installer default settings, then ORACLE_BASE is SYSTEM_DRIVE:\oracle\product\10.2.0.

If you are installing Oracle Database for Microsoft Windows on a computer with no other Oracle software installed, then you can change the ORACLE_BASE directory before running Oracle Universal Installer. Most users will not need or want to do this.

Do not change the value of ORACLE_BASE after you run Oracle Universal Installer for the first time. If there is an existing ORACLE_BASE and you change it, then there will be a conflict of Oracle base directories. If you create another ORACLE_BASE when the original ORACLE_BASE already exists, then certain tools and the database will not be able to find previously created files. They will look for them in the new ORACLE_BASE instead of the original ORACLE_BASE.

C.4.2 ORACLE_HOME Directory

The \ORACLE_HOME directory is located under SYSTEM_DRIVE:\ORACLE_BASE, where is any hard drive, and contains subdirectories for Oracle software executables and network files.

If you install Oracle Database for Windows on a computer with no other Oracle software installed and you use default settings, then the first Oracle home directory that you create is called \db_1.

C.4.3 ADMIN Directory

Database administration files are stored in subdirectories of ORACLE_BASE\ \admin\DB_NAME. Names and brief descriptions of some of these subdirectories are:

\bdump     --background process trace files
\cdump     --core dump files
\create    --database creation files
\exp       --database export files
\pfile     --initialization parameter files
\udump     --user SQL trace files

C.4.4 ORADATA Directory

Database files are stored in ORACLE_BASE\oradata\DB_NAME. Names and brief descriptions of these files are:

CONTROL01.CTL    --control file 1
CONTROL02.CTL    --control file 2
CONTROL02.CTL    --control file 3
EXAMPLE01.DBF    --EXAMPLE tablespace data files
SYSAUX01.DBF     --SYSAUX tablespace data files
SYSTEM01.DBF     --SYSTEM tablespace data file
TEMP01.DBF       --TEMP tablespace data file
USERS01.DBF      --USERS tablespace data file
*.dbf            --data files corresponding to each tablespace in your database
REDO01.LOG       --redo log file group one, member one
REDO02.LOG       --redo log file group two, member one
REDO03.LOG       --redo log file group three, member one

C.4.5 FLASH_RECOVERY_AREA Directory

The flash_recovery_area directory stores and manages files related to backup and recovery. It contains a subdirectory for each database on the system. A flash recovery area is an optional disk location that you can use to store recovery-related files such as control files and online redo log copies, archived logs, flashback logs, and Oracle Database Recovery Manager (RMAN) backups. Oracle and RMAN manage the files in the flash recovery area automatically.

C.5.1 Specifying an ORACLE_HOME Directory

To install an Optimal Flexible Architecture-compliant database, you must specify an Oracle home directory in the Path field of Oracle Universal Installer. It is of the form:

SYSTEM_DRIVE:\[PATHNAME]\oracle\product\10.2.0\ORACLE_HOME 

where:

• SYSTEM_DRIVE:\ is any hard drive. For example, c:\

• PATHNAME is an optional directory path name.

• \oracle is a mandatory directory path name, unless you changed the value of registry key ORACLE_BASE before performing the installation.

• ORACLE_HOME is the name of the Oracle home.

The following are examples of Optimal Flexible Architecture-compliant Oracle home directories:

• c:\test\oracle\product\10.2.0\db_1

• d:\oracle\product\10.2.0\db_1

C.5.2 Installing a Default Optimal Flexible Architecture Database: Example

This example shows how to create all Oracle homes within one Oracle base directory.

1. Install any Oracle Database that supports Optimal Flexible Architecture (Oracle Database release 8.1.6 or later) on a computer with no other Oracle software installed and make sure that you accept the default settings for the Oracle home (for example, c:\oracle\ora81).

2. Install any Oracle Database in a second Oracle home accepting the default settings.

Table C-1 shows the default Optimal Flexible Architecture database settings.

C.5.3 Installing a Nondefault Optimal Flexible Architecture Database: Example 1

In this example, you install Oracle Database so that each Oracle home has its own Oracle base.

1. Install any Oracle Database that supports Optimal Flexible Architecture (Oracle Database 8.1.6 or later) on a computer with no other Oracle software installed and change the default Oracle Universal Installer settings for the first Oracle home (for example, from c:\oracle\ora81 to X:\xyz).

2. Install any Oracle Database (for example, Oracle Database 10g release 1 (10.2)) in a second Oracle home and change the default Oracle Universal Installer settings for the second Oracle home (for example, from X:\xyz to Y:\abc).

Table C-2 shows the nondefault Optimal Flexible Architecture database settings for example 1.

The resulting directory tree would look similar to this:

X:\xyz                                -- Oracle home 1
     \admin
          \DB_NAME1
          \DB_NAME2
     \bin
     \network
     \oradata
          \DB_NAME1
               CONTROL01.CTL
               CONTROL02.CTL
               CONTROL03.CTL
               EXAMPLE01.DBF
               SYSAUX01.DBF
               SYSTEM01.DBF
               TEMP01.DBF
               USERS01.DBF
               REDO01.LOG
               REDO02.LOG
               REDO03.LOG
          \DB_NAME2
 Y:\abc                                -- Oracle home 2
     \admin
          \DB_NAME1
          \DB_NAME2
     \bin
     \network
     \oradata
          \DB_NAME1
               CONTROL01.CTL
               CONTROL02.CTL
               CONTROL03.CTL
               EXAMPLE01.DBF
               SYSAUX01.DBF
               SYSTEM01.DBF
               TEMP01.DBF
               USERS01.DBF
               REDO01.LOG
               REDO02.LOG
               REDO03.LOG
          \DB_NAME2

C.5.4 Installing a Nondefault Optimal Flexible Architecture Database: Example 2

In this example, you install each Oracle home into its own directory, but they all share the same Oracle base.

1. Install any Oracle Database that supports Optimal Flexible Architecture (Oracle Database 8.1.6 or later) on a computer with no other Oracle software installed and change the default Oracle Universal Installer settings for the first Oracle home (for example, from c:\oracle\ora81 to X:\xyz\oracle\abc).

2. Install any Oracle Database and change the default Oracle Universal Installer settings for the second Oracle home (for example, from c:\oracle\ora10 to X:\pqr).

Table C-3 shows the nondefault Optimal Flexible Architecture database settings for this example.

The resulting directory tree would look similar to this:

X:\pqr                         --Oracle home 2
  \bin
  \network
X:\xyz
    \oracle                    --ORACLE_BASE for both Oracle homes
      \abc                     --Oracle home 1
        \bin
        \network
      \admin
        \DB_NAME1
          \adhoc
          \bdump
          \cdump
          \create
          \exp
          \pfile
          \udump
        \DB_NAME2
          \...
      \oradata
        \DB_NAME1
          CONTROL01.CTL
          CONTROL02.CTL
          CONTROL03.CTL
          EXAMPLE01.DBF
          SYSAUX01.DBF
          SYSTEM01.DBF
          TEMP01.DBF
          USERS01.DBF
          REDO01.LOG
          REDO02.LOG
          REDO03.LOG
        \DB_NAME2

C.6.1 Disk Mirroring

You can separate and treat Oracle Database log files and database files with different levels of hardware reliability. Oracle Database log files are highly reliable because they are stored redundantly. Creating similar reliability for database files may require you to duplicate all of your data, using disk mirrors.

Disk mirroring usually involves two or more identical drives and either a hardware controller or Windows Disk Administrator. If one disk fails, then the other disks can recover data that would otherwise be lost. Using one of the disks to recover lost data may involve "breaking" the mirror. When the mirror breaks, you must build a new mirror.

Disk mirroring is part of some levels of Redundant Array of Independent Disks (RAID) configurations, provided by the disk controller. The RAID level determines the amount of redundancy. Some RAID levels can use the "hot swapping" feature, which means that you can replace a bad disk with a good one without turning off the computer or losing functionality.

C.6.2 Disk Striping

How you set up disks for use in a database depends on the number of disks and the type of hard disk controllers available. If the hard disk controllers support both striping and mirroring, then Oracle recommends you configure the controllers to support striping.

You can configure some controllers at system startup time by issuing a keyboard sequence that brings up configuration programs written by the controller manufacturer. One goal is to stripe as many drives together as possible by configuring the controllers. Each stripe shows up as one logical device.

Striping provides significant performance advantages. All the space from the striped drives appears as a single logical drive. Furthermore, the space is used by interlacing "stripes" of space from all of the disks in the stripe. This means that a large file uses some space from the first disk, then some from the second disk and so on to the last disk, and then starting back at the first disk again. Each file can be spread over all of the striped disks. Multiple CPUs can access data randomly in such a file without contention.

Controllers that support striping usually provide caching as well. This means that data can be written to the controller, and cached and saved for a time in storage not on the disk. Data that is read can be cached on the controller in a similar fashion. Read caching should not be used with Oracle Database, because all database reads are cached already in the System Global Area (SGA). The value of parameter DB_CACHE_SIZE in the initialization parameter file (init.ora) determines the buffer size that can be used in the SGA. This value also configures Oracle Database on startup.

C.6.3 Using Raw Partitions for Tablespaces

A raw partition is a portion of a physical disk that is accessed at the lowest possible level. I/O of a raw partition improves performance by approximately 5 percent to 10 percent compared to I/O of a partition containing a file system. Therefore, Oracle encourages you to use raw partitions for your tablespace files.

C.7.1 Directory Naming

Top-level names of the Optimal Flexible Architecture directory tree differ between Windows and UNIX. However, main subdirectory names and file names are the same on both operating systems.

C.7.2 ORACLE_BASE Directory

On Windows, ORACLE_BASE is associated with an Oracle home directory. ORACLE_BASE is defined in the registry (for example, in HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\KEY_HOME_NAME).

On UNIX, ORACLE_BASE is associated with a UNIX user's environment.

C.7.3 Support for Symbolic Links on Windows

The goal of Optimal Flexible Architecture is to place all Oracle software under one ORACLE_BASE directory and to spread files across different physical drives as your databases increase in size.

On UNIX, although everything seems to be in one directory on the same hard drive, files can be on different hard drives if they are symbolically linked or have that directory as a mount point.

Windows currently does not support symbolic links, so data files will not show up under a single directory as with UNIX. Instead, you may have oradata directories on multiple drives, with data files in each one. This way, you get Optimal Flexible Architecture benefits, even though data files are not all visible in a single directory.

Oracle recommends that you use one logical drive to store your database administration files and that you place other files, as needed, on other logical drives in an oradata\DB_NAME directory.

In the following example, there are four logical drives for a database named prod:

• c:\ contains an Oracle home and database administration files.

• f:\ contains redo log files. The F:\ drive could also represent two physical drives that have been striped to increase performance.

• g:\ contains one of the control files and all tablespace files. The G:\ drive could also use a RAID Level-5 configuration to increase reliability.

• h:\ contains the second control file.

The directory structure would look similar to this:

c:\oracle\product\10.2.0   --First logical drive
    \db_1                  --Oracle home
      \bin                 --Subtree for Oracle binaries
      \network             --Subtree for Oracle Net
      \...
    \admin                 --Subtree for database administration files
      \prod                --Subtree for prod database administration files
        \adhoc             --Ad hoc SQL scripts
        \adump             --Audit files
        \bdump             --Background process trace files
        \cdump             --Core dump files
        \create            --Database creation files
        \exp               --Database export files
        \pfile             --Initialization parameter file
        \udump             --User SQL trace files

f:\oracle\product\10.2.0   --Second logical drive (two physical drives, striped)
    \oradata               --Subtree for Oracle Database files
      \prod                --Subtree for prod database files
        redo01.log         --Redo log file group one, member one
        redo02.log         --Redo log file group two, member one
        redo03.log         --Redo log file group three, member one

g:\oracle\product\10.2.0   --Third logical drive (RAID level 5 configuration)
    \oradata               --Subtree for Oracle Database files
      \prod                --Subtree for prod database files
        CONTROL01.CTL      --Control file 1
        EXAMPLE01.DBF      --EXAMPLE tablespace data files
        SYSAUX01.DBF       --SYSAUX tablespace data files
        SYSTEM01.DBF       --System tablespace data file
        TEMP01.DBF         --Temporary tablespace data file
        USERS01.DBF        --Users tablespace data file

h:\oracle\product\10.2.0   --Fourth logical drive
    \oradata               --Subtree for Oracle Database files
      \prod                --Subtree for prod database files
        CONTROL02.CTL      --Control file 2