Saveset Grouping 

The SAP backup library helps to optimize the utilization of quick tape drives by combining multiple data files in savesets. Multiple file access (file multiplexing) maximizes the flow of data (streaming mode). You can define the number of files contained in each saveset with the profile parameter saveset_members or the command option brbackup -s|-savesets . The SAP backup library optimizes the distribution of the data files across the savesets in a preparation run ( backup_dev_type=rman_prep ):

  1. Estimation of the expected compression of the savesets by using BRTOOLS to determine the decompressed and compressed file sizes.
  2. BRBACKUP forms savesets and stores the information on the composition of the savesets and the compression rates for future backups in the database.

A saveset can contain individual data files, all files of a tablespace, or the complete data backup. The size of the savesets for the backup must be selected according to the tape device. A fast data flow with a minimum saveset size is the optimum. Large savesets are not recommended, since in a restoration the complete saveset has to be imported, even if only one data file is required.

saveset_members = all is set as standard for an incremental backup with the SAP backup library so that only one "incremental saveset" is created including all changed blocks.

SAP recommends that you make the preparation run once a month ( brbrackup -d rman_prep ), and each time that major changes have been made to the database, for example after a reorganization, an SAP release change, database migration or transferral of mass data. After a tablespace extension it is enough to execute the run for the newly created files only.

For more information, see Profile Parameters and BRBACKUP Command Options.