October 2, 2011

Oracle 11g R2 - RMAN compression eating up CPU resources

There have been several complaints with respect to the RMAN CPU usage on Linux on System z. At the bottom of this was always the use of the 'BASIC' compression method in RMAN.
So if your CPU is also too high during RMAN backups, consider two options:
  1. use hardware compression in your tape unit. In this case don't use compression, or if it's your corporate policy use 'NONE' as the algorithm by the following RMAN command:
    CONFIGURE COMPRESSION ALGORITHM 'NONE';
  2. Use one of the advanced compression options. My recommendation for System z is to use the 'MEDIUM' compression algorithm. This corresponds to a basic zlib compression and offers a good trade of between CPU consumption and compression ratio on System z. The required command is:
    CONFIGURE COMPRESSION ALGORITHM 'MEDIUM';
    Note that for this option you will need the "Advanced Compression Option (ACO)".
Further reading for the Oracle DBA:

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