PH23615: MESSAGE BUFFER REALLOCATION OVERLAY AND OPTIMIZATION.

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Message buffer reallocation overlay and optimization.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: Data Replication for IMS, Version 11.3       *
  *                 Data Replication for VSAM, Version 11.3      *
  ****************************************************************
  * PROBLEM DESCRIPTION: CAC00112E error due to storage overlay  *
  *                      followed by various abends.             *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  A CAC00112E error is issued during an attempt to free a memory
  allocation because the allocated area had overlain its ending
  memory picket.
  .
  The target server for IMS and VSAM was changed to isolate
  subscriptions better with APAR PH16430.  This change used an
  existing interface to allow each subscription to independently
  process its socket rather than the prior approach of managing
  all sockets open on the port collectively.  Use of the existing
  interface exposed this bug, but PH16430 did not introduce it.
  .
  The bug exposed occurs when message segmentation occurs while
  receiving the message's main message header.  The target
  server's apply service should receive the entire header first
  in order to determine if the inbound message buffer must be
  re-sized to deal with the full message length.  The code
  requested only the data from the main message header separately,
  but if less was returned continued to receive the remainder of
  the message rather than the remainder of the header.  If the
  new message exceeds the inbound message buffer length an overlay
  could occur if the second receive returns more data than fits
  in the currently allocated buffer.
  .
  At this point, the apply service would attempt to reallocate its
  inbound message buffer and if the overlay did occur would
  experience the CAC00112E during the free.  The storage is
  abandoned and processing continues since this could be a limited
  problem.  However, since the overlay may impact other control
  blocks after this allocation in storage the address space is
  likely to experience additional problems and, most likely,
  abends.
  .
  Further, it was discovered the inbound message buffer would be
  reallocated for newly received messages exceeding 64K.  The
  buffer size should increase to the largest size required and not
  continually be reallocated.
  

Problem conclusion

• The code has been modified to:
  1.  Start with a 256K buffer to avoid the need for reallocation.
  2.  Return the reallocated size to the upper level so if the
      inbound message buffer is increased further reallocations
      should be reduced.
  3.  Most importantly, the code is changed to receive the main
      message header in total before making decisions about
      reallocation needs and only then receiving the remaining
      message data to avoid possibly reading more data than will
      fit in the inbound message buffer.
  

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:

  UI68789

Modules/Macros

•    CECAPI1  CECREPL3
  

Fix information

• Fixed component name

  CLASSIC FED & E

• Fixed component ID

  5697I8200

Applicable component levels

• RB30 PSY UI68789

     UP20/04/03 P F004 Ž

Fix is available

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