PQ68122: RESTART OF TCPIP DOES NOT COMPLETE AND CAUSES ECSA STORAGE GROWTH

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Customer restarted TCPIP, initialization did not complete and
  ECSA storage began to grow.
  Fixed CSM storage was constrained so the unconditional storage
  request for a CSM dataspace message triple for ethernet padding
  in EZBIPSTR caused the task to suspend waiting for storage.
  It was holding the IPMAIN lock when it suspended. Initialization
  had completed enough that the timer task began to run.  This
  task will schedule an SRB (EZBIFOP1) to handle outbound blocking
  every time the timer pops.  The task to handle the outbound
  blocking requires the IPMAIN lock so many, many tasks became
  queued up waiting for the IPMAIN lock.  The storage for all
  these tasks caused the storage growth in TCPIP.
  VERIFICATION STEPS:
  1) CSM Fixed storage will be constrained or critical
  2) IPMAIN lock will be held by a DUCB with following calling
     sequence:
       Mod EZBSTINI
       Mod EZBSKSTO
       Mod EZBSKVRB
       Mod EZBIPSTR
       Mod EZBITSMT
       Mod EZBITSCS
       Mod EZBITDSS
  3) Many DUCBs with following calling sequence will be suspended
     waiting for the IPMAIN lock shared.
       Mod EZBITDUM
       Mod EZBIFBP1
       Mod EZBITDSS
       Mod EZBITKSS
  ADDITIONAL SYMPTOMS:
  

Local fix

• KEYWORDS: ECSA GROWTH RESTART TCPIP CSM CONSTRAINED CRITICAL
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of the Communications Server for   *
  *                 z/OS Version 1 Release 2 & 4 IP              *
  ****************************************************************
  * PROBLEM DESCRIPTION: TCPIP initialization hangs holding the  *
  *                      IPMAIN lock exclusive.  Initialization  *
  *                      has attached EZBITTUB to perform timer  *
  *                      functions.  TUB schedules an SRB to     *
  *                      run the device outbound blocking code   *
  *                      which also requires the IPMAIN lock     *
  *                      shared.  The suspended SRBs consume     *
  *                      ECSA storage to the point the schedule  *
  *                      will fail.                              *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  TCPIP stack initialization attaches the EZBITTUB timer subtask
  prior to IP streams initialization.  During IP streams setup
  an unconditional request for CSM storage is made while holding
  the IPMAIN lock exclusive.  In a CSM storage contrained
  situation, the storage request will hang until storage becomes
  available.  The TUB timer task schedules an SRB to execute the
  device outbound blocking algorithm in EZBIFOB1 on every timer
  cycle.  The EZBIFOB1 routine requests the IPMAIN lock shared
  causing the SRB to be suspended waiting on the lock.  The SRBs
  consume CSA until the stack is forced out or CSA is exhausted.
  +-------------------------------------------------------------+
  + Please check our Communications Server for OS/390 homepages +
  + for common networking tips and fixes.  The URL for these    +
  + homepages can be found in Informational APAR II11334.       +
  +-------------------------------------------------------------+
  

Problem conclusion

• EZBITTUB has been amended to only schedule the EZBIFOB1 SRB when
  the stack has completed initialization.
  
  * Cross Reference between External and Internal Names
  

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:

  UQ71989 UQ71990

Modules/Macros

• EZBITTUB
  

Fix information

• Fixed component name

  TCP/IP V3 MVS

• Fixed component ID

  5655HAL00

Applicable component levels

• R120 PSY UQ71989

     UP02/12/17 P F212

• R140 PSY UQ71990

     UP02/12/17 P F212

Fix is available

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