PM75060: IN DB2 V10 WHEN RUNSTATS OFFLOADS TO ZIIP IT CREATES DEPENDENT WLM ENCLAVES IN STC INSTEAD OF WORK-DEPENDENT ENCLAVES

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• In DB2 v10 when Runstats offloads to ZIIP it creates dependent
  WLM enclaves in STC instead of work-dependent enclaves
  This causes a problem for SAP customers who run WLM Enclaves
  and DB2 stored procedures like ADMIN_UTL_SCHEDULE
  In the reported case, a SAP ABAP program calls DB2 stored
  procedure ADMIN_UTL_SCHEDULE with max_parallel 10 and 1000
  tablespaces to process RUNSTATS.
  ADMIN_UTL_SCHEDULE calls up to 10 stored procedures DSNUTILS
  In DB2 9, there is one WLM Enclave for the SAP connection
  which executes ADMIN_UTL_SCHEDULE.
  All CPU time is aggregated into this Enclave, including CPU
  Time of RUNSTATS.
  The WLM Appl Enc Procs D6M0WLMU do not really consume CPU Time.
  In DB2 v10 there is one DDF Enclave for the ABAP connection
  and 10 extra STC Enclaves for each WLM Appl. Env Proc D6Y0WLMU,
  which executes RUNSTATS.
  The RUNSTATS CPU Time is associated to the STC Enclaves and
  not aggregated into the DDF Enclave.
  For SAP workload, customers like this classify DDF only and
  now, with Db2 v10 SAP driven workload appears in STC.
  Unfortunately, their WLM policy maps the extra STC Enclaves
  into STCHIGH, which causes performance problems for the SAP
  dialog users.
  Customers would like this to have a behavior like in DB2 v9.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All DB2 10 for z/OS utility users of         *
  *                 utilities that offload to zIIP processors    *
  ****************************************************************
  * PROBLEM DESCRIPTION: RUNSTATS always creates a new enclave   *
  *                      to off-load to zIIP processors instead  *
  *                      of executing in the current one if      *
  *                      already executing in one.               *
  ****************************************************************
  * RECOMMENDATION: Apply corrective PTF when available          *
  ****************************************************************
  When RUNSTATS can off-load to zIIP processors, it creates an
  enclave in which they will run.  When already executing in an
  enclave, it needs to schedule into that enclave.
  
  While this was reported against RUNSTATS, any utility that will
  off-load to the zIIP processors can run into this and should
  continue processing in the current enclave in which it is
  running.
  

Problem conclusion

• Utilities that off-load work into an enclave will now schedule
  into the enclave it is currently running in.  If it is not, then
  a new enclave will be created for the off-load to run in.
  

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:

  UK90599

Modules/Macros

•    DSNURBXA DSNURBXC DSNURFBR DSNURSCN DSNUSDRC
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RA10 PSY UK90599

     UP13/01/10 P F301

Fix is available

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