Oracle® Database Backup and Recovery Advanced User's Guide 10g Release 2 (10.2) Part Number B14191-02 |
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You can configure persistent settings for your channels, such as channel parameters, parallelism, and the default device type for backups. The configured settings are stored in the RMAN repository. If you configure channel settings, then you do not have to use ALLOCATE CHANNEL commands with every RMAN backup, restore, recovery or maintenance command. Configuring persistent channel settings greatly simplifies the use of RMAN.
You can always override configured channels with ALLOCATE
CHANNEL
for a particular backup job surrounded by a RUN block.
By default, RMAN has preconfigured a disk channel so that you can back up to disk without doing any manual configuration. You may, however, want to parallelize the channels for disk or tape devices to improve performance.
See Also:
"About RMAN Channels" for a conceptual overview of configured and allocated channels, and Oracle Database Backup and Recovery Reference for syntaxConfiguring parallelism for a device type specifies the number of server sessions to be used for I/O to that device type. By default, channel parallelism for each configured device is set to 1
. As a rule, allocating one channel for each physical device is best. If you are backing up to only one disk location or only one tape drive, then you need only one channel.
The CONFIGURE
DEVICE
TYPE
...
PARALLELISM
integer
command specifies how many channels (up to 254) RMAN should allocate for jobs on the specified device type. This command allocates three channels for jobs on device type DISK
:
RMAN> CONFIGURE DEVICE TYPE DISK PARALLELISM 3;
These commands back up to a media manager using two tape drives in parallel:
RMAN> CONFIGURE DEFAULT DEVICE TYPE TO sbt; # default backup device is tape RMAN> CONFIGURE DEVICE TYPE sbt PARALLELISM 2; # configure two tape channels RMAN> BACKUP DATABASE; # backup goes to two tapes, in two parallel streams
Each configured sbt
channel will back up roughly half the total data.
By default, RMAN allocates a one DISK
channel with default options, and uses it for backup commands.
Note:
This disk channel allocated by default is not the same channel as the default channel, a disk channel which RMAN creates when it first connects to the target instance, and generally does not use for activities such as backups and restores that require large amounts of I/O.However, you may want to change the default DISK
channel settings, for example, to specify a degree of parallelism or output locations for disk backups. Also, if you use a media manger, you must configure any required options for it, such as PARMS
, FORMAT
, MAXPIECESIZE
, and so forth. By configuring channel settings, you define which parameters are used for channels RMAN allocates when you use configured channels for a backup job.
Use the CONFIGURE
CHANNEL
command to configure options for DISK
and sbt
channels. CONFIGURE
CHANNEL
takes the same options used to specify one-time options with ALLOCATE
CHANNEL
.
For example, you can configure default parameters for disk and tape channels as in this example:
RMAN> CONFIGURE CHANNEL DEVICE TYPE DISK FORMAT = '?/bkup_%U'; RMAN> CONFIGURE CHANNEL DEVICE TYPE sbt PARMS='SBT_LIBRARY=/mediavendor/lib/libobk.so ENV=(NSR_SERVER=tape_svr,NSR_CLIENT=oracleclnt,NSR_GROUP=ora_tapes)';
You can configure generic channel settings for a device type, that is, a template that is used for any channels created based on configured settings for that device. If you set the PARALLELISM
for a device, and then make the device default, then RMAN uses the generic configured channel settings for each parallelized channel.
Note that if you use CONFIGURE
CHANNEL
to specify generic channel settings for a device, any previous settings are discarded, even if the settings are not in conflict. For example, after the second CONFIGURE
CHANNEL
command, which specifies only a FORMAT for configured disk channels, the MAXPIECESIZE
for the disk channel is returned to its default value:
RMAN> CONFIGURE CHANNEL DEVICE TYPE DISK MAXPIECESIZE 2G; RMAN> CONFIGURE CHANNEL DEVICE TYPE DISK FORMAT = /tmp/%U;
You can also configure default settings for individual channels from a group of parallelized channels by specifying a channel number.
The SHOW
CHANNEL
, SHOW
DEVICE
TYPE
and SHOW
DEFAULT
DEVICE
TYPE
commands are used to display the current configured channel settings.
After connecting to the target database and recovery catalog (if you use one), issue the SHOW
CHANNEL
command to display the currently configured channel settings. For example, connect the RMAN client to the target and, if applicable, the recovery catalog. Then enter:
RMAN> SHOW CHANNEL;
Sample output for SHOW
CHANNEL
follows:
RMAN configuration parameters are: CONFIGURE CHANNEL DEVICE TYPE SBT RATE 1500K;
Issue the SHOW
DEVICE
TYPE
command to display the configured devices and their PARALLELISM
and backup type settings.
To show the default device type and currently configured settings for disk and sbt devices:
After connecting to the target database and recovery catalog (if you use one), run the SHOW
DEVICE
TYPE
command. For example, enter:
SHOW DEVICE TYPE; # shows the CONFIGURE DEVICE TYPE ... PARALLELISM settings
Sample output for SHOW
DEVICE
TYPE
follows:
RMAN configuration parameters are: CONFIGURE DEVICE TYPE DISK PARALLELISM 2 BACKUP TYPE TO COPY; CONFIGURE DEVICE TYPE 'SBT_TAPE' PARALLELISM 2 BACKUP TYPE TO BACKUPSET;
Note:
As with allSHOW
commands, the output of SHOW
DEVICE
TYPE
is in the form of a valid RMAN CONFIGURE
command. You can in fact enter one command, like those shown in the preceding sample output, to configure the backup type and parallelism simultaneously. Refer to the syntax diagrams for CONFIGURE
in Oracle Database Backup and Recovery Reference for details on all of the possible ways of combining arguments to the CONFIGURE
command.Issue the SHOW
DEFAULT
DEVICE
TYPE
command to display the settings for the default device type for backups. When you issue the BACKUP
command, RMAN allocates only default channels of the type set by the CONFIGURE
DEFAULT
DEVICE
TYPE
command. This default device type setting is not in effect when you use commands other than BACKUP
. Note that you cannot disable the default device type: it is always either DISK
(default setting) or sbt
.
To show the default device type for backups:
After connecting to the target database and recovery catalog (if you use one), run the SHOW
DEFAULT
DEVICE
TYPE
command. For example, enter:
SHOW DEFAULT DEVICE TYPE; # shows the CONFIGURE DEFAULT DEVICE TYPE setting
Sample output for SHOW
DEFAULT
DEVICE
TYPE
follows:
RMAN configuration parameters are: CONFIGURE DEFAULT DEVICE TYPE TO 'SBT';
If you manually allocate a channel during a job, then RMAN disregards any configured channel settings. For example, assume that the default device type is configured to sbt
, and you execute this command:
RMAN> RUN { ALLOCATE CHANNEL c1 DEVICE TYPE DISK; BACKUP TABLESPACE users; }
In this case, RMAN uses only the disk channel that you manually allocated within the RUN
block, overriding any defaults set by using CONFIGURE
DEVICE
TYPE
, CONFIGURE
DEFAULT
DEVICE
, or CONFIGURE
CHANNEL
settings.
See Also:
"About RMAN Channels" to learn about configured and allocated channels
Oracle Database Backup and Recovery Reference for ALLOCATE
syntax
Oracle Database Backup and Recovery Reference' for CONFIGURE
syntax
Besides configuring a generic channel for a device, you can also configure one or more specific channels for each device type by manually assigning your own channel numbers to the channels. Run the CONFIGURE
CHANNEL
n
command (where n
is a positive integer less than 255) to configure a specific channel. When manually numbering channels, you must specify one or more channel options (for example, MAXPIECESIZE
or FORMAT
) for each channel. When you use that specific numbered channel in a backup, the configured settings for that channel will be used instead of the configured generic channel settings.
Configure specific channels by number when it is necessary to control the parameters set for each channel separately. This could arise in the following situations:
When running a Real Application Clusters (RAC) configuration in which individual nodes do not have access to the full set of backups, so different nodes must be configured with different connect strings so that all backups are accessible from some node
When running a Real Application Cluster and using a media manager with multiple tape drives requiring different PARMS
settings
In this example, you want to send disk backups to two different disks. Configure disk channels as follows:
CONFIGURE DEFAULT DEVICE TYPE TO disk; # backup goes to disk CONFIGURE DEVICE TYPE sbt PARALLELISM 2; # two channels used in in parallel CONFIGURE CHANNEL 1 DEVICE TYPE DISK FORMAT '/disk1/%U' # 1st channel to disk1 CONFIGURE CHANNEL 2 DEVICE TYPE DISK FORMAT '/disk2/%U' # 2nd channel to disk2 BACKUP DATABASE; # backup - first channel goes to disk1 and second to disk2
In this example, assume that you have two tape drives and want each tape drive to use tapes from a different tape pool. Configure your default output device and default sbt channels as follows:
CONFIGURE DEFAULT DEVICE TYPE TO sbt; # backup goes to sbt CONFIGURE DEVICE TYPE sbt PARALLELISM 2; # two sbt channels will be allocated by default # Assume media manager takes NSR_DATA_VOLUME_POOL to # specify a pool # Configure channel 1 to pool named first_pool CONFIGURE CHANNEL 1 DEVICE TYPE sbt PARMS 'SBT_LIBRARY=/mediavendor/lib/libobk.so ENV=(NSR_DATA_VOLUME_POOL=first_pool)'; # configure channel 2 to pool named second_pool CONFIGURE CHANNEL 2 DEVICE TYPE sbt PARMS 'SBT_LIBRARY=/mediavendor/lib/libobk.so ENV=(NSR_DATA_VOLUME_POOL=second_pool)'; BACKUP DATABASE; # first stream goes to 'first_pool' and second to 'second_pool'
When parallelizing, RMAN always allocates channels beginning with CHANNEL
1
and ending with channel number equal to the PARALLELISM
setting.
If you configure settings for a specific channel using CONFIGURE
CHANNEL
with a channel number, RMAN uses those specified configured settings. Otherwise, it uses the generic configuration for channels for that device type, as specified by the CONFIGURE
CHANNEL
command without a channel number.
Assume you enter the following channel configuration:
# disk channel configuration CONFIGURE DEVICE TYPE DISK PARALLELISM 4; CONFIGURE CHANNEL DEVICE TYPE DISK FORMAT = '/tmp/backup_%U'; CONFIGURE CHANNEL 2 DEVICE TYPE DISK MAXPIECESIZE = 20M; CONFIGURE CHANNEL 4 DEVICE TYPE DISK MAXPIECESIZE = 40M; # sbt channel configuration CONFIGURE DEVICE TYPE sbt PARALLELISM 3; CONFIGURE CHANNEL DEVICE TYPE sbt PARMS='SBT_LIBRARY=oracle.disksbt, ENV=(BACKUP_DIR=?/oradata)'; CONFIGURE CHANNEL 3 DEVICE TYPE sbt PARMS='SBT_LIBRARY=oracle.disksbt, ENV=(BACKUP_DIR=/tmp)';
The following table illustrates the channel names and channel settings that RMAN allocates when the default device is DISK
and PARALLELISM
for DISK
is set to 4
.
Channel Name | Setting |
---|---|
ORA_DISK_1 |
FORMAT = '/tmp/backup_%U' |
ORA_DISK_2 |
MAXPIECESIZE = 20M |
ORA_DISK_3 |
FORMAT = '/tmp/backup_%U' |
ORA_DISK_4 |
MAXPIECESIZE = 40M |
The following table illustrates the channel names and channel settings that RMAN allocates when the default device is sbt
and PARALLELISM
for sbt
is set to 3
.
Channel Name | Setting |
---|---|
ORA_SBT_TAPE_1 |
PARMS='ENV=(BACKUP_DIR=?/oradata)' |
ORA_SBT_TAPE_2 |
PARMS='ENV=(BACKUP_DIR=?/oradata)' |
ORA_SBT_TAPE_3 |
PARMS='ENV=(BACKUP_DIR=/tmp)' |
The PARALLELISM
setting is not constrained by the number of specifically configured channels. For example, if you back up to 20 different tape devices, then you can configure 20 different sbt
channels, each with a manually assigned number (from 1 to 20) and each with a different set of channel options. In such a situation, you can set PARALLELISM
to any value up to the number of devices, in this instance 20.
RMAN always numbers parallel channels starting with 1
and ending with the PARALLELISM
setting. For example, if the default device is sbt
and PARALLELISM
for sbt
is set to 3
, then RMAN names the channels as follows:
ORA_SBT_TAPE_1 ORA_SBT_TAPE_2 ORA_SBT_TAPE_3
RMAN always uses the name ORA_SBT_TAPE_
n even if you configure DEVICE
TYPE
sbt
(not the synonymous sbt_tape
). RMAN always allocates the number of channels specified in PARALLELISM
, using specifically configured channels if you have configured them and generic channels if you have not.
See Also:
"Automatic Channel-Specific Configurations" for concepts about manually numbered channels, and "Configuring Specific Channels: Examples"To clear a configuration is to return it to its default settings. You can clear channel and device settings by using these commands:
CONFIGURE
DEVICE
TYPE
...
CLEAR
CONFIGURE
DEFAULT
DEVICE
TYPE
CLEAR
CONFIGURE
CHANNEL
DEVICE
TYPE
...
CLEAR
CONFIGURE
CHANNEL
n
DEVICE
TYPE
...
CLEAR
(where n
is an integer)
Each CONFIGURE
...
CLEAR
command clears only itself. For example, CONFIGURE
DEVICE
TYPE
...
CLEAR
does not clear CONFIGURE
DEFAULT
DEVICE
TYPE
. The CONFIGURE
DEVICE
TYPE
...
CLEAR
command removes the configuration for the specified device type and returns it to the default (PARALLELISM
1
).
Note:
You cannot specify any other options when clearing a device type.The CONFIGURE
DEFAULT
DEVICE
TYPE
...
CLEAR
command clears the configured default device and returns it to DISK
(the default setting).
The CONFIGURE
CHANNEL
DEVICE
TYPE
...
CLEAR
command erases the channel configuration for the specified device type. RMAN does not change the PARALLELISM
setting for the device type because PARALLELISM
is specified through a separate CONFIGURE
command.
If you have manually assigned options to configured channels, then clear the options for these channels individually by specifying the channel number in CONFIGURE
CHANNEL
n
DEVICE
TYPE
...
CLEAR
. For example, assume that you run the following:
RMAN> CONFIGURE CHANNEL DEVICE TYPE DISK MAXPIECESIZE = 1800K; RMAN> CONFIGURE CHANNEL 3 DEVICE TYPE DISK FORMAT = /tmp/%U; RMAN> CONFIGURE CHANNEL 3 DEVICE TYPE DISK CLEAR;
In this case, RMAN clears the settings for CHANNEL
3
, but leaves the settings for the generic DISK
channel (the channel with no number manually assigned) intact.
See Also:
"Clearing Automatic Channel Settings "