PI75970: REQUESTED IMPROVEMENT TO STAGING SPACE FREE SPACE MANAGEMENT LOGIC TO REDUCE CPU FOR CERTAIN UR PROFILES

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Certain mixes of logged URs can produce the condition of a very
  long free chain of very small elements in the Staging Space.
  This will cause attempts to obtain free storage for a new row
  image to take significantly longer and use elevated levels of
  CPU.  This can delay replication to the point where it appears
  to stall.  An enhancement to the management of free space is
  required.
  

Local fix

• No local fix is available.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: Users of IIDR CDC for z/OS who generate very *
  *                 large URs containing data to be replicated   *
  *                 in the DB2 Log.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: The method of handling fragmented free  *
  *                      storage for the Storage Space resource  *
  *                      becomes very inefficient when the       *
  *                      number of elements on the free space    *
  *                      chain becomes high.                     *
  ****************************************************************
  * RECOMMENDATION: APPLY CORRECTIVE SERVICE                     *
  ****************************************************************
  
  The algorithm for managing free space in the Staging Space needs
  to be made more efficient.
  

Problem conclusion

• The algorithm has been improved by reducing the number of times
  that free space management accesses storage above the bar when
  looking for a suitably sized segment of free space.
  

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:

  UI46865

Modules/Macros

•    CHCCDASW CHCSTGSP HCHCA21J
  

Fix information

• Fixed component name

  INFO SRVR CDC Z

• Fixed component ID

  5655U7600

Applicable component levels

• RA21 PSY UI46865

     UP17/05/17 P F705

Fix is available

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