PM98376: HIGH VOLUME OF CPSM COWC TRANSACTIONS WHEN CICS TRANSACTION RATE REACHES 40K/S.

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Problem: High volumne of COWC transactions
  I have a benchmark that consists of 30 AORs fronted by 6 TOR.
  
  All transactions entering the TOR via LU2 terminals are
  transaction routed using CPSM sysplex optimisation.
  .
  As the workload and transaction rate increases, the volume of
  COWC transactions ( WLM MAS List Garbage Collector) is
  disproportionately high.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICSPlex SM V5R1M0 Users                 *
  ****************************************************************
  * PROBLEM DESCRIPTION:    You have a CPSM workload driven by   *
  *                      routing regions with MAXTASK set below  *
  *                      1000.  When the incoming transaction    *
  *                      rate is such that the regions are near  *
  *                      MAXTASK, you observe a high proportion  *
  *                      of COWC (CPSM WLM Garbage Collection)   *
  *                      tasks running in your routing regions.  *
  *                      The total transaction rate in target    *
  *                      regions reached 420K per minute, of     *
  *                      which 102K were COWC transactions.      *
  ****************************************************************
  * RECOMMENDATION: After applying the PTF that resolves this    *
  *                 APAR, all MASes defined as routing regions   *
  *                 in a CPSM workload must be recycled to pick  *
  *                 up the new code.  Note that regions do not   *
  *                 need to be brought down and restarted at     *
  *                 the same time.                               *
  ****************************************************************
     A target region in a CPSM workload contains a table in which
  the Transaction Data Area (TDA) and Scope Vector (WSVC) for each
  inflight routing request are anchored.  This is used for both
  CICS initiated (through DTRPGM and DSRTPGM) requests and direct
  calls to EYU9XLOP from user routing programs.  To recover table
  elements which might have been orphaned, a garbage collection
  transaction (COWC) is started if the number of free elements
  drops below a threshold value, and an instance of COWC is not
  already running.
     Prior to CICS TS V5.1, a fixed table of 1024 elements was
  allocated in each target region.  Garbage collection was trig-
  gered if the number of free elements dropped below 200.  When
  the CICS MAXTASK limit was increased in CICS TS V5.1, the size
  of the table was calculated from the value of MAXTASK at region
  startup.  For example, in a routing region with MAXTASK=200,
  the default table size was 240 elements.  However the garbage
  collection threshold value remained at 200.  Therefore a routing
  region at or near MAXTASK could be expected to have fewer than
  200 free elements at any time, and a new COWC transaction would
  be started every time EYU9XLOP was called for routing, if a COWC
  task was not already running.
  

Problem conclusion

• Module EYU0WNLM (WNLM - WLM MAS List Manager) was modified
  as follows.  If the size of the table as calculated from the
  initial MAXTASK value and the value of the WLMLCUSH EYUPARM
  (MAXTASK + (WLMLCUSH * MAXTASK) where WLMLCUSH is an EYUPARM
  specifying cushion size as a percent of MAXTASK) is less than
  1024 elements, a fixed table of 1024 elements is allocated,
  providing the same characteristics as regions running versions
  of CPSM lower than V5.1.
     If the fixed table size is used, the garbage collection
  threshold value is 1024 * WLMLCUSH.  For tables larger than
  1024 elements, the threshold is equal to the calculated cushion
  value (MAXTASK * WLMLCUSH).
     Module EYU0WDIN (WDIN - WLM Routing Initialization) was
  modified to use the garbage collection threshold value stored
  in the WLM MAS List Header rather than a fixed value of 200
  to determine whether a COWC transaction should be started.
  

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:

  UK98329

Modules/Macros

• EYU0WDIN EYU0WNLM
  

Fix information

• Fixed component name

  CICS TS Z/OS V5

• Fixed component ID

  5655Y0400

Applicable component levels

• R80M PSY UK98329

     UP13/10/20 P F310

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.