PH68303: ENHANCEMENT FOR MAXIMUM EXTENTS ERROR MESSAGE AND EXTEND FAILURE PROCESSING

Obtain the fix for this APAR.

APAR status

• Closed as new function.

Error description

• Insert performance can be highly impacted due to maximum
  extents reached and insert transaction performs the same
  extend request and exhaustive space search.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All Db2 13 for z/OS users                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: 1. Enhance Db2 to issue DSNP031I        *
  *                      message in certain intervals when a     *
  *                      data set of the page set is             *
  *                      approaching the maximum number of       *
  *                      extents                                 *
  *                      2. Remove the respective exhaustive     *
  *                      space search when maximum number of     *
  *                      extents is reached                      *
  ****************************************************************
  Currently, Db2 only issues message DSNP031I when a data set is
  almost at the maximum number of extents; no warning is
  provided until maximum extents is reached. For a multi-volume
  data set (either non-SMS or SMS managed without the SMS data
  class Extent Constraint Removal (ECR) attribute enabled), that
  maximum is only 255 extents. The lack of warning means that
  DBAs do not have adequate time to take action in order to
  prevent extend failure. In addition, when extend fails,
  subsequent transactions continue to request extends which
  triggers exhaustive space search. As a result, contention can
  occur and further cause performance degradation.
  

Problem conclusion

Temporary fix

Comments

• Db2 has been modified such that DSNP031I warning message is
  issued at 70% of maximum extents and at each incrementing 5%
  interval. Furthermore, when a data set reaches the maximum
  number of extents, subsequent extend requests will recognize
  the limit and no longer continue to perform exhaustive
  search. However, the best course of action to prevent extent
  limitations is to convert to SMS data sets with Extent
  Constraint Removal (ECR) attribute enabled, thus increasing
  the maximum number of extents to 7257.
  

APAR Information

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

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

  UO06348

Modules/Macros

• DSNISFAS DSNISFPI DSNISGSC DSNISRTI DSNISUPI DSNPXTN0 DSNPXTRC
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RD10 PSY UO06348

     UP25/12/31 P F512  

Fix is available

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