RMAN settings when using ProtecTIER deduplication

Answer

When using Data Protection for Oracle to backup the data to a ProtecTier VTL, it is important that the data is not changed during the backup process so that deduplication can process the data effectively.

The recommendation is to ensure that files are not multiplexed within the backup data, as this can cause the data to appear unique, thereby limiting the amount of deduplication that can occur. The suggestion is to setup RMAN with FILESPERSET=1 so that each object will be sent individually. This would allow any files that have not changed and have existing (identical) data to achieve a higher deduplication ratio.

This suggestion for using a value of 1 for the FILESPERSET parameter is based on how Oracle will manage the data being backed up. When including multiple files in the same Oracle backupset, they will be multiplexed together, which means that the data blocks from all of the datafiles in the backup set are interspersed with one another. ProtecTIER will have a better dedup ratio when the data is not multiplexed. and this multiplexing of the data can be avoided by limiting the backupset to have only 1 file within it (ie, FILESPERSET=1).

The Data Protection for Oracle product can accommodate the ProtecTIER suggested configuration within the RMAN script. For example a relatively generic script would contain the FILESPERSET parameter as part of the backup command:
run
{
allocate channel t1 type 'sbt_tape' parms
'ENV=(TDPO_OPTFILE=/ora11/tdpo.opt)';
allocate channel t2 type 'sbt_tape' parms
'ENV=(TDPO_OPTFILE=/ora11//tdpo.opt)';
..... ----> allocate more channels here based on the number of sessions to be used for the backup
backup
FILESPERSET 1
(database);
}