Databases Reference
In-Depth Information
preconfigures a disk channel for you by default. If you're using tape drives, you'll have to configure the channels,
whether explicitly in the RMAN run blocks or by using automatic channel configuration. Automatic channel
configuration is the way to go in most cases; it makes life easy for you because you don't have to manually allocate the
channels each time you perform a backup, restore, or recovery task.
You can configure persistent channel settings to simplify your usage of RMAN by using the
configure channel
commands shown earlier in this recipe. These persistent channel settings are stored in the RMAN repository, thus
making it unnecessary for you to use the
allocate channel
command with each RMAN
backup
,
recovery
,
restore
, or
maintenance
command. RMAN first looks for any generic settings you might have set for any channel you don't explicitly
configure. If you haven't manually set any channel configurations, RMAN will use the automatic channel configuration.
You use the
clear
option with the
configure
command to clear any automatic channel settings. You must use a
separate
configure ... clear
command to set the configuration back to its default value. Here are some examples:
RMAN> configure default device type clear; # reverts to the default
device type (DISK)
RMAN> configure channel device type sbt clear; # erases all
options that were set for the sbt channel
RMAN> configure channel 1 device type disk clear; # erases
configuration values set specifically for channel 1.
There is a difference between how RMAN treats a
backup
or
copy
command and a
restore
command when it
comes to the allocation of channels. Even if you configure automatic channels for sbt, if your default disk type is disk,
RMAN will allocate only disk channels when you run a
backup
or
copy
command. If you want RMAN to use the sbt
channel, you have to use one of the following two methods:
•
Use the allocate channel command in a run block to allocate the sbt channel.
backup
command.
•
Specify the device type as disk directly within the
By default, RMAN sends all backups to the fast recovery area if you've already configured one. That is, you don't
have to expressly specify the location by using the
forma
t option of the
configure channel
command. However,
sometimes you may want to bypass the fast recovery area and send the RMAN backups elsewhere to disk. You can
do so by explicitly configuring a backup device type with a specific
format
option. In the following example, we
show how you can use the
configure channel device type disk format
command to specify that all RMAN disk
backups be made to the /backup directory:
RMAN> configure channel device type disk format '/backup/ora_df%t_s%s_s%p';
In the format specification:
%t
stands for four-byte timestamp.
•
%s
stands for the backup set number.
•
%p
stands for the backup piece number.
If you use the
configure
command as shown in the previous example, all RMAN backups will be made in the
/backup directory, even if you've configured a fast recovery area and there is plenty of free space in it. Thus, you must
be prepared to lose the benefits of having the fast recovery area when you use the
configure channel device type
disk format
command shown previously.
You can also send the backups to an automatic storage management (ASM) disk group, as shown in the following
example:
•
RMAN> configure channel device type disk format '+dgroup1';
All backups will now be stored in the ASM disk group +dgroup1.
