Use
When you back up the Oracle database with the
Oracle Recovery Manager (RMAN), the SAP backup library helps to optimize the utilization of fast tape drives by combining multiple data files in save sets. Multiple file access – also known as "file multiplexing" – maximizes the flow of data to keep tape drives in streaming mode.Prerequisites
You can define the number of files contained in each save set with the
saveset_members parameter from the initialization Profile init<DBSID>.sap or the BRBACKUP command option -s|-savesets.For a preparation run, set the
backup_dev_type parameter to rman_prep.For an incremental backup with the SAP backup library, the
saveset_members parameter is internally set to all so that only one "incremental save set" is created including all changed blocks.Features
The SAP backup library optimizes the distribution of the data files across the save sets in a preparation run as follows:
The following graphic shows this:
A save set can contain from one to four individual data files, all files of a tablespace, or the complete data backup. The size of the save sets for the backup must be selected according to the tape device. A fast data flow with a minimum save set size is the optimum. Large save sets are not recommended, since in a restore the complete save set has to be read, even if only one data file is required.
Activities
SAP recommends that you perform the preparation run once a month – using the BRBACKUP command
–d|-device with the rman_prep parameter – and each time that major changes have been made to the database, for example after a reorganization, an SAP release change, database migration, or mass data import. 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.