PH25576: MQ Z/OS: A SMALL STORAGE LEAK OCCURS IN SP0 WHEN A CLIENT CONNECTS TO A GROUP LISTENER AND IS REJECTED DUE TO MAXINST

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• A small storage leak occurs when a client channel connects to a
  group listener and is then rejected because the channel has
  reached its MAXINST value:
    CSQX489E Maximum instance limit limit exceeded, channel
             <channel-name> connection <conn-id>
  
  As part of the set-up of the channel connection, a 240 byte
  (xF0) area of storage is allocated to hold information about
  the shared channel status (XSCS control block). When the CHIN
  determines that the channel cannot start due to MAXINST, it
  frees the resources allocated for the channel, but it does not
  release the XSCS storage.
  
  The storage is in Subpool 0 Key 8 (SP0 KEY8 K8).
  

Local fix

• N/A
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of IBM MQ for z/OS Version 9       *
  *                 Release 0 Modification 0, Release 1          *
  *                 Modification 0 and Release 2 Modification 0. *
  ****************************************************************
  * PROBLEM DESCRIPTION: If a shared channel is prevented from   *
  *                      starting due to exceeding MAXINST,      *
  *                      MAXINSTC or MAXCHL, then a 240 byte     *
  *                      memory leak may occur in the CHINIT.    *
  *                                                              *
  *                      This will be accompanied by messages    *
  *                      CSQX489E, CSQX490E and CSQX513E for     *
  *                      MAXINST, MAXINSTC and MAXCHL            *
  *                      respectively.                           *
  ****************************************************************
  When starting a shared channel, a shared status entry is written
  to DB2 to provides status information about the connection
  throughout the QSG. If the connection is ultimately rejected due
  to exceeding MAXINST, MAXINSTC or MAXCHL, then the shared status
  entry is subsequently deleted from DB2. The code then attempts
  to free the in-memory copy, but does this incorrectly resulting
  in the storage being leaked.
  

Problem conclusion

• The faulty logic has been corrected to free the shared status
  entry correctly.
  

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:

  UI75377 UI75379 UI75380

Modules/Macros

• CMQXRMSA CSQXRMSS
  

Fix information

• Fixed component name

  IBM MQ Z/OS V9

• Fixed component ID

  5655MQ900

Applicable component levels

• R000 PSY UI75380

     UP21/05/29 P F105 ¢

• R100 PSY UI75379

     UP21/05/29 P F105 ¢

• R200 PSY UI75377

     UP21/05/29 P F105 ¢

Fix is available

• Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.