PH45363: MQ Z/OS: IMPROVE DIAGNOSTICS FOR AN INVALID DUPLICATE MESSAGE ON SYSTEM.CHANNEL.SYNCQ

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• SYSTEM.CHANNEL.SYNCQ contains messages with sequence number and
  Unit Of Work information about channels. There are times when
  an invalid duplicate message is created, which can cause
  channel problems such as:
  
  CSQX517E CSQXSUPR Error in SYSTEM.CHANNEL.SYNCQ
  - channel [channel-name] repeated
  
  CSQX526E CSQXRESP Message sequence error for channel
  [channel-name], sent=[seq-num-1] expected=[seq-num-2]
  
  This APAR is raised to investigate better diagnostics to help
  find the root cause of the duplicate messages.
  .
  Additional information:
  ----------------------
  With this APAR applied, CSQX517E occurs both earlier and more
  frequently than before. After this fix, the CSQX517E message is
  issued each time a duplicate is detected when the syncq record
  for the channel is updated.  The CSQSNAP information and dump
  are only created for the first incidence of a duplication for
  any given channel. The frequency of messages depends on how
  often the sync queue needs updating, for example depending on
  the persistence and syncpoint characteristics of the channel. In
  the time between a duplicate being detected and CSQ4SUTL being
  run to correct it, it is possible to temporarily suppress the
  messages until the next queue manager restart by issuing the SET
  SYSTEM EXCLMSG(X517) command. CSQ4SUTL is a utility that can be
  provided by the Support Center.
  

Local fix

• The RESET CHANNEL command will allow the channel to start.
  However, if there is still an invalid duplicate record, the
  channel will fail again the next time it starts.
  
  The Support Center can assist with safely removing the invalid
  duplicate record from SYSTEM.CHANNEL.SYNCQ.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of IBM MQ for z/OS Version 9       *
  *                 Release 2 Modification 0 and                 *
  *                 Release 3 Modification 0.                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: CSQX517E is issued on channel initiator *
  *                      startup, and CSQX526E is issued on      *
  *                      channel startup due to duplicate        *
  *                      records for a channel on                *
  *                      SYSTEM.CHANNEL.SYNCQ                    *
  ****************************************************************
  The presence of a duplicate sync queue record for a channel is
  detected when rebuilding the sync queue index at channel
  startup, or when an inconsistent sequence number is detected
  during channel startup.
  This can be a significant time after the duplicate record was
  erroneously created, preventing the cause of the duplicate
  record from being identified.
  

Problem conclusion

• Additional checking is added when updating a channel's syncq
  record to detect duplicate records must sooner and capture
  diagnostic information to aid in problem diagnosis:
  
  The first time a duplicate record is detected for
  a given channel, an FFST is written by rriWriteSync to the
  CSQSNAP DD and a 5C6-00E70022 dump at CSQXRCTL.FFST(90001601) is
  captured.
  Message CSQX517E is also issued, identifying the affected
  channel, each time the duplicate record is detected.
  

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:

  UI81627 UI81628

Modules/Macros

• CSQXRSYN
  

Fix information

• Fixed component name

  IBM MQ Z/OS V9

• Fixed component ID

  5655MQ900

Applicable component levels

• R200 PSY UI81628

     UP22/08/03 P F208

• R300 PSY UI81627

     UP22/08/03 P F208

Fix is available

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