Accuracy of real-time statistics

In general, the real-time statistics values are very accurate. However, several factors can affect the accuracy of the statistics.

The following factors might affect the accuracy of real-time statistics values:

• Certain utility restart scenarios.
• A utility failure that leaves the object in a utility-in-progress state (UTRW, UTRO, or UTUT).
• Certain utility operations that leave indexes in a database restrictive state, such as RECOVER-pending (RECP). Always consider the database restrictive state of objects before accepting a utility recommendation that is based on real-time statistics.
• Certain third-party vendor solutions that do not correctly manage real-time statistics.
• A Db2 subsystem failure.
• A notify failure in a data sharing environment.
• Counts that exceed the numeric limits of the data types for the real-time statistics catalog table columns. The values in the following SYSIBM.SYSTABLESPACESTATS columns cannot be greater than 2147483647, although the internal counters can exceed that value:
  • REORGINSERTS
  • REORGUPDATES
  • REORGDELETES
  • STATSINSERTS
  • STATSUPDATES
  • STATSDELETES

  The same limitation does not apply to the TOTALROWS column because its data type is BIGINT and its value is calculated from the in-memory counters.

If you think that some statistics values might be inaccurate, you can correct the statistics by invoking the REORG, RUNSTATS, or COPY utilities for the database objects that are described by the inaccurate statistics.