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DB2 Database Logging Performance

The number of parallel streams that the DB2 for z/OS environment can support is often limited more by the DB2 logging throughput rate than by anything else. The commit process waits for a successful write to the active log and, if there is contention on the logs, performance suffers. Possible solutions to ease bottlenecks caused by logging performance include:

  • Increase the number of output buffers for writing active log data sets. The size of the output buffer can be changed using the DSNZPARM parameter, OUTBUFF.
  • Increase the active log size. If logs fill up faster than they can be archived, performance suffers.
  • Determine the optimal number of DB2 active logs based on peak EIM loads, plus a cushion.
  • Place the active log data sets on separate dedicated volumes.
  • Place archive logs on a virtual tape system (VTS), or on disk, if VTS is not available.
  • Define all table spaces (base tables and interface tables) with compression, which reduces logging, and decreases I/O.
  • Consider data sharing if a single subsystem cannot handle the logging tasks.
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