PI06478: EZBITDSA ABEND 4C5 74FF2500 ABEND0C4 EZBUDBYP SP241 TCP ECSA DUCB DUSA SHORTAGE PORT 12001 UCB LOCK

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Outbound traffic backed up on port 12001 waiting on the UCB
  lock.  The lock contention is causing DUCB expansion and
  suspended SRBs that quickly exhaust ECSA.  The current
  design that requires serializing EE outbound requests on a
  given port is unable to sustain high volume traffic.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of the IBM Communications Server   *
  *                 for z/OS Version 1 Release(s) 12 and 13 IP:  *
  *                 Enterprise Extender (EE)                     *
  ****************************************************************
  * PROBLEM DESCRIPTION: Enterprise Extender (EE) outbound       *
  *                      traffic causes lock content, resulting  *
  *                      in ECSA SP241 storage growth.  Storage  *
  *                      exhaustion leads to abend 4C5 74FF2500  *
  *                      and abend 0C4.                          *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  Enterprise Extender (EE) has a large number pipes and/or ANR
  routed traffic sending high volumes of data outbound.  The EE
  data path for a given network priority will serialize on a
  single UDP port.  The lock contention on the UCB lock for that
  port results in numerous suspended SRBs.  Each suspended SRB
  has an ECSA backed 12K DUCB associated with it.  The delays
  resulting from the lock contention can trigger retransmissions
  that exacerbate the lock contention and ECSA usage.
  When ECSA becomes exhausted further DUCB expansion will fail
  with an abend 4C5 74FF2500 and the outbound data represented
  in the abending request will be dropped.  Additional symptoms
  include an abend 0C4 when VTAM is unable to allocate the
  storage area used to pass data to TCP/IP, resulting in EZBUDBYP
  using an invalid storage address.
  +-------------------------------------------------------------+
  + 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

• EZBUDBYP has been enhanced to detect UCB lock contention every
  15 outbound requests.  When lock contention is detected the UCB
  lock is released and reobtained to allow the waiting SRBs to
  process.
  
  Consider applying VTAM APAR OA43910 to reduce the number of
  SRBs scheduled to EZBUDBYP to process EE traffic.  There is no
  dependency on the fix for OA43910 when applying this fix.
  
  * 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:

  PI06564 UI14528 UI14529

Modules/Macros

• EZBDGCMR EZBDGDUA EZBDGDUC EZBITKCB EZBUDBYP
  EZB2LKTB ITLOCK
  

Fix information

• Fixed component name

  TCP/IP V3 MVS

• Fixed component ID

  5655HAL00

Applicable component levels

• R1C0 PSY UI14528

     UP14/02/18 P F402

• R1D0 PSY UI14529

     UP14/02/18 P F402

Fix is available

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