IT31828: STATISTICS COLLECTED WITH INDEX SAMPLING MAY PRODUCE INACCURATE REAL-TIME INDEX STATISTICS AND MON_GET_INDEX INFORMATION

Db2 Version 11.1 Mod 4 Fix Pack 6 for Linux, UNIX, and Windows
Db2 Version 11.1 Mod 4 Fix Pack 6 for Linux, UNIX, and Windows

APAR status

• Closed as program error.

Error description

• This may be due to RUNSTATS .. INDEXSAMPLE, Real-Time Statistics
  (RTS) running with index sampling or AUTO_RUNSTATS running with
  index sampling.
  
  All index statistics sourced from catalog tables are accurate
  and unaffected.
  
  Inaccurate index statistics could be returned by MON_GET_INDEX
  and RTS statistics fabrication.
  
  Non-fabricated/fully collected RTS statistics are not affected.
  
  An example of MON_GET_INDEX providing a different NLEAF count
  relative to that seen in SYSCAT.INDEXES after a RUNSTATS with
  INDEXSAMPLE:
  
      RUNSTATS ON TABLE DB2INST1.TEST AND INDEXES ALL INDEXSAMPLE
  SYSTEM(10)
      DB20000I  The RUNSTATS command completed successfully.
  
      SELECT NLEAF FROM TABLE(MON_GET_INDEX('DB2INST1','TEST',-1))
  
      NLEAF
      --------------------
                        24
  
        1 record(s) selected.
  
  
      SELECT NLEAF FROM SYSCAT.INDEXES WHERE TABNAME='TEST'
  
      NLEAF
      --------------------
                       250
  
        1 record(s) selected.
  

Local fix

• Avoid use of RUNSTATS with the INDEXSAMPLE clause.
  
  Disable Auto Sampling using the database config parameters,
  AUTO_SAMPLING.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * ALL                                                          *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * See Error Description                                        *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * Apply v11.1 Mod 4 Fixpack 6 to DB2 database server           *
  ****************************************************************
  

Problem conclusion

• First fixed in v11.1 Mod 4 Fixpack 6
  

Temporary fix

• SEE LOCAL FIX
  

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  DB2 FOR LUW

• Fixed component ID

  DB2FORLUW

Applicable component levels

• RB10 PSN

     UP