APAR status

• Closed as program error.

Error description

• VTAM issued the following messages:   IST1000I STORAGE
  UNAVAILABLE IN SYSTEM GETVIS LOC-BELOW AREA and IST154I
  EXPANSION FAILED FOR IO BUFFER POOL - CODE 2, USERID=***NA***.
  Code 2 indicates that not enough storage is available in the
  System GETVIS area for expansion. In a few minutes time, CICS
  issued thousands of DFH2411I termid tranid time nodeid ATTEMPTED
  INVALID LOGON messages.  The HOTIOTRM start option was enabled,
  but no IST930I nodename1 nodename2 SESSION USING percentage OF
  IOBUF messages were displayed.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All using VTAM boundary function.            *
  ****************************************************************
  * PROBLEM DESCRIPTION: HOT I/O condition results in IOBUF      *
  *                      pool expansion failure.                 *
  *                      24-BIT SYSTEM GETVIS EXHAUSTED          *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  The problem is summarized as follows:
  1) A local LU is flooding VTAM with BIND requests for an
     application residing on this host.
  2) The BINDs are rejected by the application with SESSIONC.
  3) This results in an UNBIND type '0F'x flowing to the LU.
  4) The BSB for the session is cleaned up, but an IO buffer is
     allocated by ISTTSCB2 and queued to the
     ATCVT_BLBTSCB_CHAIN queue.
  5) The ATCVT_BLBTSCB_CHAIN queue is processed by the
     Wake-Up PAB (ISTTSCWU) when it runs.
  6) The Wake-Up PAB can take up to three seconds to run.  The
     local LU is sending in BINDs fast enough that the buffer
     expansion is needed before Wake-Up runs to process this
     queue.  This leads to an excess number of IO buffers
     being accumulated leading to a SYSTEM GETVIS storage
     shortage.
  

Problem conclusion

• TPADDEL - Modified to support the QCOUNTER option which
            maintains a depth counter for the associated queue.
  TPREMEL - Modified to support the QCOUNTER option which
            maintains a depth counter for the associated queue.
  ISTTSCB2,
  ISTTSCBG - Added QCOUNTER to the TPADDEL invocations for the
             ATCVT_BLBTSCB_CHAIN.  Also, code will schedule
             the Wake-Up PAB if the ATCVT_BLBTSCB_CHAIN depth
             exceeds an internal threshold.
  ISTTSCWU - Added QCOUNTER to the TPREMEL invocation for the
             ATCVT_BLBTSCB_CHAIN.
  ISTATCVT - Defined ATCVT_BLBTSCB_Cnt to hold the current
             count of BLBs and TSCBs on the ATCVT_BLBTSCB_CHAIN.
             Defined ATC_BLBTSCB_QDepth_Threshold as
             CONSTANT(100).
  ISTBSCRT - Included for maintenance purposes.
  

Temporary fix

• *********
  * HIPER *
  *********
  

Comments

APAR Information

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

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

  UD53552

Modules/Macros

•    ISTATCVT ISTBSCRT ISTTSCBG ISTTSCB2 ISTTSCWU
  TPADDEL  TPREMEL
  

Fix information

• Fixed component name

  VTAM V4 VSE/ESA

• Fixed component ID

  568606501

Applicable component levels

• RFE6 PSY UP

     DY47096

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Product categories:

Software

Networking

Enterprise Connectivity

VTAM for VSE/ESA and VM/ESA

All

Software version:

FE6

Reference #:

DY47096

IBM Group:

Software Group

Modified date:

2009-12-03