PI80854: FURTHER IMPROVEMENT TO THE STAGING SPACE FREE SPACE MANAGEMENT LOGIC TO REDUCE THE CPU INCURRED 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.  This is in addition to the improvements provided by
  APAR PI75970.
  

Local fix

• No local fix is available
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: Users who replicate large numbers of large   *
  *                 URs with a large mix of tables over a short  *
  *                 period of time.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: When the Staging Space is subjected to  *
  *                      a flow of a large number of table rows  *
  *                      of various sizes, the length of a chain *
  *                      of free areas can grow excessively. The *
  *                      logic that manages the chain of free    *
  *                      areas does not scale well for very      *
  *                      large numbers.  Excessive CPU is used   *
  *                      while the subscription appears to stall *
  *                      without sending any data to the target. *
  ****************************************************************
  * RECOMMENDATION: APPLY CORRECTIVE SERVICE                     *
  ****************************************************************
  
  When processing large numbers of varying sizes of row changes,
  the CPU use of the address space can rise excessively coupled
  with no data being sent to the target.
  

Problem conclusion

• The method used to obtain free space for use has been changed
  to a best fit algorithm.  The method used to access the free
  chain has been changed from linear to logarithmic.
  

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:

  UI49172

Modules/Macros

•    CHCIISDL CHCMBARA CHCMBCHS CHCMBCHT CHCMBDAN
  CHCMBDES CHCMBDEU CHCMBELL CHCMBENG CHCMBENP CHCMBENU CHCMBESP
  CHCMBFIN CHCMBFRA CHCMBFRB CHCMBFRC CHCMBFRS CHCMBHEB CHCMBISL
  CHCMBITA CHCMBITS CHCMBJPN CHCMBKOR CHCMBNLB CHCMBNLD CHCMBNOR
  CHCMBPTB CHCMBPTG CHCMBRMS CHCMBRUS CHCMBSVE CHCMBTHA CHCMBTRK
  CHCMBZZZ CHCOSCIQ CHCSDTPF CHCSTGSP HCHCA21J
  

Fix information

• Fixed component name

  INFO SRVR CDC Z

• Fixed component ID

  5655U7600

Applicable component levels

• RA21 PSY UI49172

     UP17/08/04 P F708

Fix is available

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