IT27072: Memory leak in IBM MQ on Linux after a queue is emptied

APAR status

• Closed as program error.

Error description

• IBM MQ keeps details of queued messages in shared memory
  and in some cases this memory is not freed completely when it
  should
  be.  For example, issuing "CLEAR QLOCAL" against a queue which
  was previously
  open but has since been closed.
  

Local fix

• This problem only affects queues containing more than 8192
  messages and so avoiding deep queues is one workaround.
  

Problem summary

• ****************************************************************
  USERS AFFECTED:
  Users on Linux with deep queues are more likely to be affected
  by this problem.
  
  
  Platforms affected:
  Linux on Power, Linux on S390, Linux on x86, Linux on x86-64,
  Linux on zSeries
  
  ****************************************************************
  PROBLEM DESCRIPTION:
  Over a period of time the amount of shared memory that is being
  used by IBM MQ may be seen to be growing in an uncontrolled
  manner.  This was caused by a gcc compiler upgrade which
  introduced an optimisation that affected the way that IBM MQ
  behaves when removing internal queue meta-data.
  

Problem conclusion

• The affected IBM MQ code has been modified so that aggressive
  loop optimisation does not modify intended behaviour.
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
  Version    Maintenance Level
  v9.0 LTS   9.0.0.7
  v9.1 CD    9.1.2
  v9.1 LTS   9.1.0.2
  
  The latest available maintenance can be obtained from
  'WebSphere MQ Recommended Fixes'
  http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006037
  
  If the maintenance level is not yet available information on
  its planned availability can be found in 'WebSphere MQ
  Planned Maintenance Release Dates'
  http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006309
  ---------------------------------------------------------------
  

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:

Fix information

• Fixed component name

  IBM MQ BASE M/P

• Fixed component ID

  5724H7261

Applicable component levels