PM05249: CIST TASK LEFT HANGING ATTEMPTING TO TERMINATE AN IPCONN AFTER PM01878 ( UK52920 ) 10/01/15 PTF PECHANGE

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• While an IPIC attached task is procesing a SYNCPOINT request
  from a remote partner, there is a connection error which
  causes a CIST task to be attached to terminate the IPCONN.
  The CIST task issues a wait to allow the task which owns the
  IPCONN session to terminate and release its RECEIVE ISSB.
  When the user task tries to send its SYNCPOINT response it
  should receive a PURGED response due to the state of the
  IPCONN session.
  However due to code changed by PM01878, the send of the
  syncpoint response does not receive a purged response. This
  causes issb_rfp (the receive forget pending flag) to be switched
  on by DFHISUOW.
  When the user task releases its IPCONN receive session, it is
  left on the active session chain. A forget flow will never
  arrive so the session will never be full released and the CIST
  task is left hanging forever.
  The IPCONN is left in FREEING ( FRE ) state.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users with PM01878 applied.              *
  ****************************************************************
  * PROBLEM DESCRIPTION: An IPCONN is left in FREEING ( FRE )    *
  *                      state and a CIST task hangs following   *
  *                      an IPCONN connection error.             *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  A mirror task which is attached over an IPIC connection from a
  partner CICS region gets suspended in end-of-task syncpoint.
  During this delay the partner region terminates the IPCONN
  when the IPIC TCPIPSERVICE is IMMCLOSED.
  This causes the CISE (IPIC error task) to be resumed in the
  region where the mirror task is suspended.
  CISE sets the isss_sess_error flag to indicate that the
  connection to the IPIC partner is no longer usable.
  CISE attaches a CIST task for TERMINATE_CONNECTION.
  The CIST TERMINATE_CONNECTION function performs cleanup for
  the IPIC connection and discovers that there is still an
  active session being used by the suspended mirror task.
  CIST suspends cleanup, waiting for the session to be released
  to the free pool by the mirror task.
  The mirror task now runs and attempts to send a syncpoint
  response to the IPIC partner region.
  DFHISSR routine dfhissr_check_session_usable should detect
  that the connection to the partner is unusable and return a
  PURGED response.
  However, changes made by PM01878 mean that the PURGED response
  is no longer returned. The failure to return a PURGED response
  means that the ISSB_RFP flag (forget pending) is switched on
  in the session control block.
  When the mirror task terminates it releases the session but the
  ISSB_RFP flag causes it to be placed on the active chain instead
  of the free chain. This means that the waiting CIST task is
  never resumed and the freed session sits on the active chain
  waiting for a forget flow which will never arrive.
  

Problem conclusion

• UK52920
  DFHISSR has been changed to correct the routine which checks
  if an IPCONN session is in a usable state.
  

Temporary fix

• FIX AVAILABLE BY PTF ONLY
  

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

  UK56267

Modules/Macros

• DESISSR  DFHISSR
  

Fix information

• Fixed component name

  CICS TS Z/OS V4

• Fixed component ID

  5655S9700

Applicable component levels

• R600 PSY UK56267

     UP10/04/28 P F004

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.