Creating Oracle Duplexed Backup Sets


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.