Dell Avamar for Oracle 19.10 User Guide

RMAN tuning options

Backups that you perform with the Avamar Plug-in for Oracle in Avamar Administrator use RMAN. RMAN reads the individual data files, bundles the files into backup sets, and then sends the backup set to avtar.

To create the backup set, RMAN simultaneously reads multiple files from the disk, and then writes the blocks of file data into the same backup set. The combination of blocks from multiple files is called backup multiplexing. The following figure shows the multiplexing of three files into a backup piece.

In Figure 1, RMAN simultaneously reads three files and writes them to the backup set intermingled. The RMAN multiplexing feature intermingles the backup files, and does not provide the data stream in a similar format for subsequent reads.

Because of how the RMAN multiplexing feature intermingles files, backups by the Avamar Plug-in for Oracle to the Avamar server can contain the duplicate data even if no changes were made to the database since the last backup. The RMAN multiplexing feature can negatively affect the data deduplication ratio of the Avamar Plug-in for Oracle.

The Avamar Plug-in for Oracle improves data deduplication performance by enabling you to use the Filesperset option in Avamar Administrator.

The Filesperset option specifies the number of files to include in each backup set. The default value of the Filesperset option is 1. When you specify a value for the Filesperset option, RMAN uses the value as a limit for the number of files RMAN includes in a backup set.