Duplexing 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 (for example, 0tcm8u2s_1_1 and 0tcm8u2s_1_2).

In most cases, the easiest method 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 will automatically put each copy onto a separate medium (for example, a separate tape).

Note that it is not possible to duplex backup sets to the flash recovery area, and that duplexing only applies to backup sets, not image copies. It is an error to specify the BACKUP... COPIES when creating image copy backups, and the CONFIGURE... BACKUP COPIES setting is ignored for image copy backups.

Duplexing Backup Sets with CONFIGURE BACKUP COPIES

The CONFIGURE ... BACKUP COPIES command specifies 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. You must have automatic channels configured.

To duplex a backup with CONFIGURE BACKUP COPIES:

Configure the number of copies on the desired device type for datafiles and archived redo logs on the desired device types. This example configures duplexing for datafiles and archived logs on tape as well as duplexing for datafiles (but not archived logs) on disk:

RMAN> CONFIGURE DEVICE TYPE sbt PARALLELISM 1;
RMAN> CONFIGURE DEFAULT DEVICE TYPE TO sbt;
RMAN> CONFIGURE CHANNEL DEVICE TYPE DISK FORMAT '/save1/%U', '/save2/%U';
RMAN> CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE sbt TO 2;
RMAN> CONFIGURE ARCHIVELOG BACKUP COPIES FOR DEVICE TYPE sbt TO 2;
RMAN> CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 2;

Execute the BACKUP command. The following command backs up the database and archived logs to tape, making two copies of each datafile and archived redo log:
```
RMAN> BACKUP DATABASE PLUS ARCHIVELOG; # uses default sbt channel
```
Because of the configured formats for the disk channel, the following command backs up the database to disk, placing one copy of the backupsets produced in the /save1 directory and the other in the /save2 directory:
```
RMAN> BACKUP DEVICE TYPE DISK AS COPY DATABASE;
```
Issue a LIST BACKUP command to see a listing of backup sets and pieces. For example, enter:
```
RMAN> LIST BACKUP SUMMARY;
```
The #Copies column shows the number of backupsets, which may have been produced by duplexing or by multiple backup commands.

Duplexing Backupsets with BACKUP... COPIES

The COPIES option of the BACKUP command overrides every other COPIES or DUPLEX setting to control duplexing of backupsets.

To duplex a backup with BACKUP COPIES:

Specify the number of identical copies with the COPIES option of the BACKUP command. For example, run the following to make three copies of each backup set in the default DISK location:
```
RMAN> BACKUP AS BACKUPSET DEVICE TYPE DISK 
  COPIES 3 
  INCREMENTAL LEVEL 0 
  DATABASE;
```
Because you specified COPIES on the BACKUP command, RMAN makes three backupsets of each datafile regardless of the CONFIGURE DATAFILE COPIES setting.
Issue a LIST BACKUP command to see a listing of backup sets and pieces (the #Copies column shows the number of copies, which may have been produced through duplexing or through multiple invocations of the BACKUP command). For example, enter:
```
RMAN> LIST BACKUP SUMMARY;
```