OA40581: JES3 CPU SPIKE

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• External symptoms:
  CPU monitors shows JES3 using excessively more CPU than
  normal, customer running with Netserv
  
  Impact to customer:
    system performance slow
  
  Analysis:
    An SVC dump taken at the time of the spike show the TCP and
  MSGC FCT's processing slowly, searching for matching selection
  criteria for the Netservs.  The system has a large number of
  jobs in output service, each OSE is being searched.  The
  algorithm used to search is inefficient.
  Verification steps:
  1) JES3 CPU usage higher than normal
  2) SVC dump of JES3 address space significant number of external
  interrupts in the system trace under module IATOSBM
  
  The projected closing code is PER for releases HJS7770 and up.
  

Local fix

• Stop all Netservs except for one to reduce contention.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of HJS7770 and HJS7780.            *
  ****************************************************************
  * PROBLEM DESCRIPTION: High CPU utilization by JES3 TCP/IP.    *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  The customer noticed periods of high CPU utilizations lasting
  sometimes for several hours.  Several dumps were taken during
  the problem period.  A JMF was also run and the report was
  provided to IBM.
  
  The documentation analysis showed the Get routine in module
  IATOSBM taking a big percentage of the overall JES3 Nuc task CPU
  usage.
  
  The selection algorithm in that routine was such that it
  searched through all Resqueue (RQ - IATYRSQ) control blocks to
  find one with TCP/IP NJE (or BDT) output.  But only a very small
  fraction of the RQs contained TCP/IP output.  Moreover, due to
  competing TCP NJE FCTs (IATYFCT), the code kept re-scanning the
  chain.
  

Problem conclusion

• Installation On (Global)
               Order (Any)
  Activation   Order (Any)
               Type/JES3 restart (Hot)
               Type/IPL (None)
               CLPA (No)
  (See Apar II07968 for definitions)
  
  Code in the Get routine of module IATOSBM was changed to only
  search the TCP (or BDT) chain of OSE (IATYOSE) control blocks.
  That will significantly reduce the search code path and the
  CPU usage by the TCP FCT (IATYFCT).
  
  APAR OA40581 prereq's (and sup's) for FMID HJS7770:
  Pre's: * NONE *
  
  APAR OA40581 prereq's (and sup's) for FMID HJS7780:
  Pre's: * NONE *
  

Temporary fix

• *********
                      * HIPER *
                      *********
  *** * TEMPORARY FIX MAY BE OBTAINED FROM DLL OR INFO/ACCESS ****
  ******************* OA40581  DECK AVAILABLE ********************
  

Comments

APAR Information

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

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

  UA67496 UA67497

Modules/Macros

• IATOSBM
  

Fix information

• Fixed component name

  JES3

• Fixed component ID

  5752SC1BA

Applicable component levels

• R770 PSY UA67496

     UP12/12/28 P F212

• R780 PSY UA67497

     UP12/12/28 P F212

Fix is available

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