PH68870: S5C6-00E20001 ABENDS

APAR status

• Closed as program error.

Error description

• The abends occurred because the group command server in CSQNGRS
  made a storage request for a negative amount of bytes, due to an
  incorrect group command reply handling in CSQNGRS2. Group
  command replies arrive on the command list header. Because these
  are Group commands, they are usually sent via XCF notifications.
  However, they can also be sent via the QMGR's command list
  header if there is an XCF buffer or path shortage.
  
  Turns out that a batch of replies are being split between those
  sent via XCF, and those sent via the command list header. This
  can result in CSQNGRS2 processing the replies in the incorrect
  order, and abending with S5C6-00E20001.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of IBM z/OS for MQ Version 9       *
  *                 Release 4 Modification 0.                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: Abend S5C6-00E20001 in CSQSVBK, or      *
  *                      Abend 0C4 in CSQNGRS2 occurs following  *
  *                      an XCF buffer shortage.                 *
  ****************************************************************
  An XCF buffer shortage caused queue sharing group command
  messages between two queue managers to be sent using the Command
  List Header on the Admin Structure instead of using XCF.
  After 10s the affected queue switched back to sending messages
  using the default XCF method. However at the point it switched
  back a batch of command responses for a remote command (issued
  on another queue manager with CMDSCOPE) was in the process of
  being sent.
  This led to the responses unexpectedly arriving out of order,
  resulting in the reported abends when processing them.
  

Problem conclusion

• When switching from using the Admin Structure to XCF for command
  message responses, any responses groups in progress will
  continue to be sent using the Admin Structure to preserve
  ordering.
  

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:

  PH73179 UO09804

Modules/Macros

• CSQEWCMQ CSQNGRS1
  

Fix information

• Fixed component name

  IBM MQ Z/OS V9

• Fixed component ID

  5655MQ900

Applicable component levels