PM74874: UNEXPECTED SPACE GROWTH OF PBG UTS TABLE SPACE, WHEREBY ONLY 1 PAGE PER SEGMENT WAS ACTUALLY USED.

APAR status

• Closed as program error.

Error description

• Unexpected space growth of PBG UTS tablespace with SEGSIZE=64,
  whereby only 1 page per segment was actually used. This apar
  applies to any defined SEGSIZE for PBG, but the growth is very
  noticeable with SEGSIZE=64. Rapid growth was also seen with PBG
  Member Cluster and will be addressed in this apar.
  

Local fix

• Reduce the SEGSIZE and increase REORG frequency.
  
  
  
  
  
  
  
  
  
  
  
  
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Problem summary

•   USERS AFFECTED: All DB2 10 z/OS users of Partition By
                    Growth table spaces with and without
                    MEMBER CLUSTER.
  
    PROBLEM DESCRIPTION: When using PBG table spaces it is
                         possible to see only the first page
                         in a segment being used before going
                         to another new segment.  This caused
                         rapid growth of the table space.
  
    RECOMMENDATION:
  
  In the non MEMBER CLUSTER case a small timing window could cause
  getting a new segment to occur multiple times consecutively,
  which would result in just the first page of the new segment to
  be used.  This would then leave the rest of the segment empty.
  
  In the MEMBER CLUSTER case, during an UPDATE operation if there
  was no room for the newly updated record in its current
  partition, it would then search the first Space Map page of the
  next partition before it asked for a new segment.  When multiple
  updates occur at the same time, each update would ask for a new
  segment resulting in only the 1st page of each segment being
  used.
  

Problem conclusion

• In the non MEMBER CLUSTER case the timing window has been
  shortened so that this scenario is less likely to occur.
  
  In the MEMBER CLUSTER case after searching the 1st Space Map
  page we will search the last segment before asking for a new
  segment.
  

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:

  UK95206

Modules/Macros

• DSNISGNS DSNISGSC DSNISUPI
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RA10 PSY

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