OA56774: NEW FUNCTION - AVOID MONOPOLIZATION OF COUPLING FACILITY RESOURCES BY A SINGLE STRUCTURE

Obtain the fix for this APAR.

APAR status

• Closed as new function.

Error description

• New function
  

Local fix

• N/A
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * Installations at z/OS V2R2 (HBB77A0) and                     *
  * above, exploiting parallel sysplex with                      *
  * workloads producing a high rate of coupling                  *
  * facility (CF) activity.                                      *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * A workload that generates a high rate                        *
  * of CF activity can monopolize CF                             *
  * resources, impeding other work and                           *
  * seriously degrading sysplex                                  *
  * performance.                                                 *
  *                                                              *
  * E8561/K                                                      *
  * SYSPLEXDS                                                    *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * This PTF will not be fully effective on the                  *
  * system to which it is being applied until                    *
  * the PTF(s) for this APAR are applied to all                  *
  * systems in the sysplex.                                      *
  *                                                              *
  * Install the applicable PTF on each system in                 *
  * the sysplex.  A rolling IPL is sufficient to                 *
  * activate the support.                                        *
  ****************************************************************
  When CF requests directed to a single structure consume a
  disproportionate share of CF resources, workloads targeting
  other structures may be starved of resources and unable to
  achieve acceptable service times and throughput.  The
  degradation can affect critical system components and middleware
  applications across the entire sysplex.  A mechanism for reining
  in a runaway application and preventing CF resource
  monopolization is required.
  

Problem conclusion

Temporary fix

Comments

• OA56774, in conjunction with coupling facility control code
  level (CFLEVEL) 24, provides new function to prevent a runaway
  sysplex application from monopolizing a disproportionate share
  of CF resources.
  
  Each time z/OS directs a command to a CF at CFLEVEL 24, the CF
  will inform z/OS whether the target structure is monopolizing CF
  resources.  z/OS will assess whether sustained monopolization is
  occurring and, when appropriate, will limit requests directed to
  the monopolizing structure.  Throttling CF requests associated
  with the abusive workload will allow other sysplex workloads to
  achieve acceptable performance.
  
  Some factors that, separately or in combination, may cause a
  workload to monopolize CF resources are:
  
  o An unusually high CF request rate.
  
  o A high degree of contention for CF structure objects.  For
    example, the application may be designed or configured in
    such a way that a large number of requests target
    a small number of lists or lock table entries.
  
  o System-managed duplexing (because CF resources are held
    longer while the two CFs exchange signals to coordinate
    updates).
  
  Each system in the sysplex monitors and reacts to monopolization
  independently based on the results of that system's CF requests.
  
  To activate this support, installations must enable the new
  XCF optional function CFMONOPAVOID, using either the COUPLExx
  parmlib member or the SETXCF FUNCTIONS command:
  
  COUPLExx
  
    FUNCTIONS ENABLE(CFMONOPAVOID)
  
  SETXCF
  
    SETXCF FUNCTIONS,ENABLE=CFMONOPAVOID
  
  The CFMONOPAVOID function is disabled by default.  IBM
  recommends that installations with high-traffic CF workloads
  enable this function on all systems in the sysplex.
  
  Although each system in the sysplex monitors and reacts to
  monopolization independently, it is necessary that the OA56774
  support be installed and activated on all systems in the sysplex
  to be fully effective on any system.  It is possible for one
  system that initiates a low volume of CF requests (system A) to
  observe monopolization caused by another system that initiates a
  high volume of requests (system B).  If the OA56774 support is
  installed and activated on system A but is not installed or not
  activated on system B, system A's decision to throttle CF
  requests to the affected structure will have little effect on
  the monopolization state of the CF.  The high volume of requests
  from system B will continue to monopolize CF resources,
  potentially causing a performance degradation affecting all
  systems.
  
  Documentation updates
  =====================
  
  Publication updates associated with this APAR can be found at
  http://publibz.boulder.ibm.com/zoslib/pdf/OA56774.pdf
  
  Summary of updates:
  
  z/OS MVS Data Areas Vol 3 (ITK-SCE) GA32-0937
  ---------------------------------------------
  o IXCYQUAA
    o New feature bit QuReqRfAMDALevel4
  
  o IXLYAMDA
    o New flag IXLYAMDSTRL_MS defined in IXLYAMDSTRL
    o New flag IXLYAMDSTRC_MS defined in IXLYAMDSTRC
    o New DSECTs IXLYAMDSTRL4 and IXLYAMDSTRC4
  
  o IXLZSTRB
    o New flag StrBStrDetailStrMonopState defined in StrBStrDetail
  
  
  z/OS MVS Data Areas Vol 2 (IAX-ISG) GA32-0936
  ---------------------------------------------
  o IHADWHDR
    o New flag DwhdrStrMonopState defined in DWHDR
  
  
  z/OS MVS Setting Up a Sysplex SA23-1399
  ---------------------------------------
  o Section "Planning Parmlib Members for a Sysplex" -> "Planning
    the COUPLExx Member in Parmlib" -> "The FUNCTIONS Statement"
  
    Table 1 "XCF / XES Optional Functions" updated to describe the
    new CFMONOPAVOID function.
  
  
  z/OS MVS Programming: Sysplex Services Guide SA23-1400
  ------------------------------------------------------
  o Section "Sysplex Services for Communication (XCF)" -> "Using
    the Cross-System Coupling Facility (XCF)" -> "Obtaining XCF
    Information" -> "Using the IXCQUERY Macro" -> "Information
    Returned Inline to IXCQUERY"
  
    Document new feature bit QuReqRfAMDALevel4.
  
  o Section "Coupling Facility Accounting and Measuring Services"
    -> "Using IXLMG" -> "Types of Information Available"
  
    Document new IXLYAMDA DSECTs IXLYAMDSTRL4 and IXLYAMDSTRC4.
  
  
  z/OS MVS Programming: Sysplex Services Reference SA38-0658
  ----------------------------------------------------------
  o Section "IXLMG - Coupling Facility Measurement"
  
    Description updated to reference new IXLYAMDA DSECTs
    IXLYAMDSTRL4 and IXLYAMDSTRC4.
  
    AMDALEVEL parameter updated for AMDALEVEL=4.
  
  
  z/OS MVS System Messages Vol 10 (IXC-IZP) SA38-0677
  ---------------------------------------------------
  o IXC357I
  
    New optional function name CFMONOPAVOID.
  
  o IXC360I
  
    New EXCEPTIONAL CONDITIONS and MONOPOLIZING CF RESOURCES lines
    in DISPLAY XCF,STRUCTURE output.
  
  o IXC362I
  
    Structures listed as allocated in the displayed CF may be
    flagged to indicate exceptional conditions.
  
  o IXL055I and IXL056I
  
    New lines REQUESTS QUEUED FOR NO SUBCHANNEL and REQUESTS
    QUEUED TO AVOID CF MONOPOLIZATION.
  
  o IXL062E
  
    New message reporting the start of monopolization management
    for a structure.
  
  o IXL063I
  
    New message reporting the end of monopolization management
    for a structure.
  
  o IXL064I
  
    New message reporting monopolization management status for a
    structure.
  

APAR Information

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

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

  UJ03201 UJ03202 UJ03203 UJ03204 UJ03227 UJ03228

Modules/Macros

• IXLE1RTY IXCO1DC3 IXLM2DIE IXLM2SR  IXCM2LX2 IXLYDLIC IXLR1ALR
  IXCI2RIM IXLF1VTT IXCYQUAA IXLA1SLM IXLR1RRS IXLM2CR  IXLF1ASD
  IXCXCFEN IXLIXLJP IXLC3DSN IXLM2TAM IXLX1EER IXLM2BRK IXLYAMDA
  IXLF1LCR IXCM2MS2 IXLIXLEN IXLM2SG  IXLM1MS2 IXLC3LFN IXLX1AEI
  IXCM2MS3 IXLA1MG  IXLF1TX2 IXLM2SP  IXLE1MEV IXLM2DSP IXLM2MR
  IXLM1TMR IXLR1GRT IXLM2XRQ IXLYDCAC IXCM2FMS IXLM1REC IXLM1MST
  IXCM2MST IXLF1STS IXCI2PH1 IXLM2DRS IXLM2DRR IXLF1TF6 IXLM1TBL
  IXLF1FAX IHADWHDR IXLE1REC IXLR1SYN IXLM2XSR IXLZSTRB IXCXCFJP
  IXCM2FNP IXLR1CAC IXLF1FAT IXCF1INT IXLM2DR  IXLR1LST IXLI1SIN
  IXLF1VME IXLMG    IXCM2PRS
  

Fix information

• Fixed component name

  CROSS SYS.EXT.S

• Fixed component ID

  5752SCIXL

Applicable component levels

• R7BJ PSY UJ03203

     UP20/06/24 P F006  

• R7CJ PSY UJ03204

     UP20/06/24 P F006  

• R7A0 PSY UJ03227

     UP20/06/24 P F006  

• R7B0 PSY UJ03201

     UP20/06/24 P F006  

• R7AJ PSY UJ03228

     20/06/24 P F006

• R7C0 PSY UJ03202

     UP20/06/24 P F006  

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.