PH05298: CONCURRENCY REQUIRED PROGRAM SWITCHES TO CO TCB FOR ACCESSES TO DFHTEMP

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Concurrency Required programs running on an OPEN TCB switch to
  the Concurrent ( CO ) TCB for accesses to DFHTEMP. This causes
  increased wait time to single thread for the CO TCB when they
  should stay on the OPEN TCB. Note this occurs when SUBTSKS=1
  is coded in DFHSIT.
  

Local fix

• Code DFHSIT parameter SUBTSKS=0
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICS users                               *
  ****************************************************************
  * PROBLEM DESCRIPTION: Unnecessary switching to the CO TCB     *
  *                      when performing I/O to DFHTEMP.         *
  ****************************************************************
  DFHTSAM handles auxiliary temporary storage operations.
  Procedure TSBIOC calls VSAM to perform the I/O operations to
  DFHTEMP. The code switches to the CO TCB for the duration of the
  calls to VSAM. For tasks executing under the QR TCB, this is
  valid as it prevents blocking operations from stopping CICS.
  However, for tasks that call temporary storage under their
  own open TCB, this is unnecessary. It is a cost in terms of
  execution time and CPU, and a bottleneck of forcing all
  requests to serialise on one TCB.
  KEYWORDS: OTE required concurrency threadsafe threadsafety.
  

Problem conclusion

• DFHTSAM has been changed to only switch to the CO TCB for its
  I/O operations if the calling task is running on the QR TCB.
  

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:

  UI61227 UI61228 UI61229 UI61230 UI61231

Modules/Macros

• DFHTSAM
  

Fix information

• Fixed component name

  CICS TS Z/OS V5

• Fixed component ID

  5655Y0400

Applicable component levels

• R000 PSY UI61231

     UP19/02/12 P F902

• R100 PSY UI61229

     UP19/02/12 P F902

• R200 PSY UI61230

     UP19/02/12 P F902

• R800 PSY UI61228

     UP19/02/16 P F902

• R900 PSY UI61227

     UP19/02/27 P F902

Fix is available

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