A fix is available
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 number
OA56774
Reported component name
CROSS SYS.EXT.S
Reported component ID
5752SCIXL
Reported release
7A0
Status
CLOSED UR1
PE
NoPE
HIPER
NoHIPER
Special Attention
YesSpecatt / New Function / SYSPLXDS /
Xsystem
Submitted date
2019-01-11
Closed date
2020-06-09
Last modified date
2020-07-06
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
GA320937XX | SA231399XX | SA231400XX | SA380658XX | SA380677XX |
GA320936XX |
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
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Document Information
Modified date:
07 July 2020