PH07227: NO I/O BUFFERING FOR DB2 ARCHIVE LOG READS WHEN NOT READING FROMTHE FIRST VOLUME OF A MULTI-VOLUME DATA SET ON DASD

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Db2 may stop using I/O buffering when reading forward on a
  multi-volume archive log dataset on disk.
  The part of the archive log dataset that is on the first volume
  will use buffering, but parts on other volumes will not.
  This can affect log read I/O performance of Db2 archive logs
  reads of multi-volume archive log datasets on disk, when the log
  is read in a forward manner, such as reading the log via IFI 306
  requests, or during the log apply phase of the RECOVER utility
  (except for the backout part if that is needed).
  This does NOT apply to archive logs on tape, nor compressed
  archive logs on disk.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All Db2 for z/OS users.                      *
  ****************************************************************
  * PROBLEM DESCRIPTION: Slower archive log read may be          *
  *                      encountered when the Db2 archive log is *
  *                      a multi-volume (DASD) data set.  This   *
  *                      performance issue may happen in IFI     *
  *                      read, RECOVER, or any utility reading   *
  *                      the archive logs in a forward           *
  *                      direction.                              *
  ****************************************************************
  * RECOMMENDATION: Apply corrective PTF when available.         *
  ****************************************************************
  When reading logs from the second or subsequent volume of a
  multi-volume archive log data set on DASD, log manager switches
  to single buffer read.  Db2 uses multiple buffer reads for
  reading logs on the first volume.  The switching may affect the
  log read performance.
  
  The performance degradation is only applicable to archive log
  read in forward direction.
  
  The problem is not applicable to archives which are striped data
  sets, compressed data sets, single volume data sets, or on tape.
  

Problem conclusion

• The code is fixed by resetting the single buffer read control
  flag when accessing the second or subsequent volume of the
  archive log set.
  

Temporary fix

Comments

APAR Information

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

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

  UI61329 UI61330

Modules/Macros

•    DSNJR008
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RB10 PSY UI61330

     UP19/02/27 P F902

• RC10 PSY UI61329

     UP19/02/27 P F902

Fix is available

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