RMAN can
make up to four copies of a backup set simultaneously, each an exact duplicate
of the others. A copy of a backup set is a copy of each backup piece in the
backup set, with each copy getting a unique copy number
In most
cases, the easiest method of duplexing backup sets is to use BACKUP...COPIES or
CONFIGURE ... BACKUP COPIES to duplex backup sets. For DISK channels, specify
multiple values in the FORMAT option to direct the multiple copies to different
physical disks. For sbt channels, if you use a media manager that supports
Version 2 of the SBT API, then the media manager automatically puts each copy
onto a separate medium (for example, a separate tape).
Note: The System Backup to Tape (SBT) API
is the interface defined for Media Management Library (MML) developers, so that
they can provide MMLs that communicate with RMAN.
Note that
it is not possible to duplex backup sets to the Flash Recovery Area, and that
duplexing applies only to backup sets, not image copies. You receive an error
if you specify the BACKUP... COPIES option when creating image copy backups.
The CONFIGURE...BACKUP COPIES setting is ignored for image copy backups.
Duplexed
backup sets are typically used for tape backups.
Creating
Duplexed Backup Sets Using CONFIGURE BACKUP COPIES
Use the
CONFIGURE ... BACKUP COPIES command to specify the number of identical backup
sets that you want to create on the specified device type. This setting applies
to all backups except control file autobackups (because the autobackup of a
control file always produces one copy) and backup sets when backed up with the
BACKUP BACKUPSET command.
Note: You must have automatic channels
configured.
To create a
duplexed backup set with CONFIGURE
BACKUP COPIES, perform
the following steps:
1. Configure the number of copies on the
desired device type for data files and archived redo log files.
2. Execute the BACKUP command.
3. Issue a LIST BACKUP
command to verify your backup.
Note: The last BACKUP command
is not affected by the COPIES configuration setting. It creates a single copy
to disk.
RMAN> CONFIGURE
ARCHIVELOG BACKUP COPIES
2> FOR DEVICE TYPE sbt
TO 2;
RMAN> CONFIGURE
DATAFILE BACKUP COPIES
2> FOR DEVICE TYPE sbt
TO 2;
RMAN> BACKUP DATABASE
PLUS ARCHIVELOG;
RMAN> BACKUP DEVICE
TYPE DISK AS COPY DATABASE;
Creating
Duplexed Backup Sets Using BACKUP COPIES
You can use the BACKUP command with the COPIES option to override other COPIES or DUPLEX
settings to create duplexed backup sets.
To duplex a backup with BACKUP COPIES, perform the following steps:
1. Specify the number of identical copies with the COPIES option of the
BACKUP command.
2. Issue a LIST BACKUP command to verify your backup.
Creating
Backups of Backup Sets
Use the RMAN BACKUP BACKUPSET command to back up previously created backup sets.
Only backup sets that were created on device type DISK can be backed up using
RMAN. The backup sets can be backed up to any available device type.
The BACKUP
BACKUPSET command uses the default disk channel to copy backup sets from disk to
disk. To back up from disk to tape, you must either configure or manually
allocate a nondisk channel.
Backing
Up Read-Only Tablespaces
Because
read-only tablespaces are not being written to, there is no need to continually
back them up as you do read/write tablespaces. You can use the SKIP READONLY
option of the BACKUP command to let RMAN know to not back up read-only
tablespaces.