Databases Reference
In-Depth Information
The size of the change tracking file is not proportional to the number of updates in the database. Instead, the size
of the file depends on how large the database is, the number of data files, and how many threads of redo are enabled.
Initially, the change tracking file starts at 10MB and grows in 10MB increments. Since RMAN allocates 320KB of space
in the change tracking file for each data file in the database, a database with a very large number of data files would
require a larger allocation of space for the change tracking file than a database with a small number of data files.
Creating Multiple Backup Sets
Problem
You want to initiate a backup and have RMAN automatically make multiple copies of the resulting backup set. You
don't want to make any persistent configuration changes to your RMAN environment.
Solution
You can specify the making of multiple copies (duplexing) of backup sets by using the
backup
command's
copies
option or by issuing the
set backup copies
clause in a
backup
command. The following example shows how to use
the
copies
option to make multiple backup copies. Of course, you need to tell RMAN where the multiple destinations
for the duplexed backups are by using the
format
option. Here's our example:
RMAN> backup
copies 2
database
format '/u01/app/oracle/backup/db_%U',
'/u02/app/oracle/backupdb_%U';
In the example shown here, the
copies
parameter produces two backups of the database, each on a different
disk, with disk locations being specified by the
format
parameter.
The next example shows how to use the
set backup copies
command to make two backup copies of the
database:
run
{
allocate channel c1 device type sbt
parms 'ENV=(OB_DEVICE_1=testtape1,OB_DEVICE_2=testtape2)';
set backup copies = 2;
backup database plus archivelog;
}
The OS environment variables specific to Oracle Secure Backup (OSB), such as OB_DEVICE_1, must be in
uppercase. Otherwise, the corresponding OSB job will not be restricted to a specific drive. Instead, the corresponding
OSB job will use whatever tape drive is available, which is the default behavior.
■
if you want to duplex your backups when using a tape device, you must enable the
backup_tape_io_slaves
initialization parameter on the target database you are backing up.
Note
