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PK70646: TASK WITH THREADSAFE PROGRAMS THAT DO SQL CALLS AND LOTS OF FILE CONTROL CALLS USES MORE CPU AND HAS MORE TCB SWITCHES AT CICS3.2

A fix is available

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APAR status

  • Closed as program error.

Error description

  • There is a threadsafe program that makes some SQL calls and
    lots of File Control calls to a file that is a shared data
    table.  Being a shared data table, CICS must be on the QR TCB
    to process the request.  (The same would be true of an NSR
    file and also, if not z/OS 1.9 or higher, LSR files.)
       Since migrating to CICS/TS 3.2, this program uses more CPU
    and has lots more TCB switches than it did at a prior release
    of CICS.
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All                                          *
    ****************************************************************
    * PROBLEM DESCRIPTION: Response time degradation when          *
    *                      threadsafe applications repeatedly call *
    *                      file control.                           *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    A threadsafe (but not openapi) program called DB2 and so was
    switched to an L8 TCB. It then called file control. The
    file was defined as a shared data table, and such requests
    are not threadsafe to CICS. This meant that DFHFCFR had to
    switch to QR for the duration of the request. However, it
    then switched back to the caller's old TCB mode upon exit
    from DFHFCFR. For many such calls to file control, the
    application was being switched from L8 to QR and back to L8
    again. This led to an increase in CPU usage, and a
    rise in response time for the application to complete.
    Note: the same problem applies to other types of file which
    require the use of QR, such as BDAM files and remote files.
    Keywords: SDT CICSPERF performance PK45354
    

Problem conclusion

  • DFHFCFR routine ACCMTEST has been changed to avoid switches back
    to the caller's TCB mode upon completion of the request, if the
    caller was a threadsafe CICSAPI program that did not require to
    be executed under an open TCB. This brings file control into
    line with other parts of CICS that have to switch to the QR TCB
    to process non-threadsafe EXEC CICS commands.
    

Temporary fix

  • FIX AVAILABLE BY PTF ONLY
    

Comments

APAR Information

  • APAR number

    PK70646

  • Reported component name

    CICSTS V3 Z/OS

  • Reported component ID

    5655M1500

  • Reported release

    500

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2008-08-15

  • Closed date

    2008-10-16

  • Last modified date

    2008-11-03

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

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

    UK40779

Modules/Macros

  •    DESFCCM  DFHFCCMS DFHFCDMS DFHFCFR  DFHFCLMS
    

Fix information

  • Fixed component name

    CICSTS V3 Z/OS

  • Fixed component ID

    5655M1500

Applicable component levels

  • R500 PSY UK40779

       UP08/10/21 P F810

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.

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Document Information

Modified date:
03 November 2008