PI72631: LOCK CONTENTION WHEN CSM STORAGE GOES CONSTRAINED

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• .
  A system goes constrained on CSM storage (IVT5592I CSM FIXED
  STORAGE AT CONSTRAINED LEVEL or IVT5591I CSM ECSA STORAGE AT
  CONSTRAINED LEVEL message).  The potential exists for some
  processing of inbound data that is being distributed to another
  system to issue an unconditional request for CSM data while
  holding the IPMAIN lock shared.  This processing will get
  suspended waiting for the CSM storage to become available.  If
  later processing needs the IPMAIN lock exclusive, a significant
  portion of TCPIP processing will become suspended waiting for
  the IPMAIN lock, causing a growth in DUCBs in TCPIP private and
  ECSA.  This could continue until various ABENDs start occurring.
  For example:
  
   - EZZ9679E TCPIP CSM HAS BEEN CRITICAL FOR AT LEAST xxxx
     SECONDS
  
   - IST2273E PACKETS DISCARDED FOR TCPIP - READ QUEUE CONGESTION
  
   - EZZ9670E TCPIP  SYSPLEX PROCESSING HAS ENCOUNTERED A
     NONRECOVERABLE ERROR
  
   - S4C5/74502506 ABENDs
  
  
  Verification:
  
   - CSM storage is in a constrained state.
  
   - The DUCBs holding the IPMAIN lock will have a call pattern
     similar to the following:
  
        RSA  7F3EC7B8  Prev 24815380  Next 7F3EC8E8  Mod EZBIFRC1
        RSA  7F3EC8F0  Prev 7F3EC7B8  Next 7F3EDA28  Mod EZBIFINB
        RSA  7F3EDA30  Prev 7F3EC8F0  Next 7F3EEFA8  Mod EZBIPINB
        RSA  7F3EEFB0  Prev 7F3EDA30  Next 7F3F0178  Mod EZBXFUT3
        RSA  7F3F0180  Prev 7F3EEFB0  Next 7F3F0408  Mod EZBITSMT
        RSA  7F3F0410  Prev 7F3F0180  Next 7F3F08D8  Mod EZBITSCS
        RSA  7F3F08E0  Prev 7F3F0410  Next 00000000  Mod EZBITDSS
  
     These DUCBs will be on the itsto_ducb_uncond queue.
  
  
  Keywords:
  
  Defects 53336 & 53452
  

Local fix

• .
   - Ensure that there is sufficient Fixed CSM storage defined for
     the system's workload.  See TechNote 1216034 for more
     information:
  
        http://www.ibm.com/support/docview.wss?uid=swg21216034
  
     If sufficient real storage is available, dynamically
     increasing the limit may relieve the problem:
  
        MODIFY vtamname,CSM,FIXED=xxxM
  
   - Improve Sysplex Distributor performance by:
  
     - Adding VIPAROUTEs for the target systems.
  
     - Adding ADJUSTDVIPAMSS ALL is specified on the GLOBALCONFIG
       statement for all target systems.  For z/OS 2.1, ensure
       that UI28533 has been applied first.
  
     - Adding QDIOACCELERATOR to the IPCONFIG statement.  Ensure
       that the PTF for PI66075 has been applied first.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * All users of the IBM Communications Server                   *
  * for z/OS Version 2 Releases 1 and 2 IP:                      *
  * Sysplex Distributor                                          *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * lock contention when CSM storage is contrained               *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * apply PTF                                                    *
  ****************************************************************
  Sysplex Distributor function is making unconditional CSM storage
  requests while holding locks causing lock contention
  

Problem conclusion

• change Sysplex Distributor CSM storage requests to be
  conditional
  

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:

  UI43289 UI43290

Modules/Macros

• EZBIPINB EZBXFUT3 EZB6PINB EZBCTFME EZBX6UT3 EZBXFCFS
  

Fix information

• Fixed component name

  TCP/IP V3 MVS

• Fixed component ID

  5655HAL00

Applicable component levels

• R220 PSY UI43290

     UP17/02/13 P F702

• R210 PSY UI43289

     UP17/02/13 P F702

Fix is available

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