IT33894: SourceTransferStartExits can be invoked twice for the same managed transfer.

APAR status

• Closed as program error.

Error description

• An IBM MQ Managed File Transfer agent is configured to run a
  SourceTransferStartExit at the start of every managed transfer.
  The design of the SourceTransferStartExit means that it only
  expects to be run once for each managed transfer. If the exit
  detects that it is has been run more than once for a managed
  transfer, the exit returns an ResultCode of CANCEL.
  
  Very occasionally, the SourceTransferStartExit is run twice for
  the same managed transfer. This causes the exit to return a
  CANCEL ResultCode, which results in the managed transfer being
  marked as "Failed".
  

Local fix

• n/a
  

Problem summary

• ****************************************************************
  USERS AFFECTED:
  This issue affects users of IBM MQ Managed File Transfer who
  have agents configured to run SourceTransferStartExits at the
  beginning of managed transfers.
  
  
  Platforms affected:
  MultiPlatform
  
  ****************************************************************
  PROBLEM DESCRIPTION:
  When a source agent receives a managed transfer request, it
  performs the following steps:
  
  - Resolve the transfer item specification into a list of
  transfer items (files or messages) to transfer.
  - Run any SourceTransferStartExits.
  - Run any preSource programs or commands.
  - Contact the destination agent for the managed transfer, and
  perform the transfer negotiation.
  
  A destination agent can only act as the destination agent for a
  certain number of managed transfers at any one time. This is
  specified by the agent property "maxDestinationTransfers". If it
  is already acting as the destination agent for this number of
  managed transfers when it receives a new transfer negotiation
  request, it sends a reply back to the source agent indicating
  that it is currently too busy to participate in the new managed
  transfer.
  
  When the source agent receives this reply, it puts the managed
  transfer into a WaitingForDestinationCapacity state, and adds it
  to its backlog. After the time period specified by the agent
  property "senderTransferRetryInterval" has elapsed, the source
  agent resumes the managed transfer and sends a new transfer
  negotiation request to the destination agent again, to see if it
  is now able to participate in it.
  
  Now, in this situation, the source agent would incorrectly run
  any SourceTransferStartExits before contacting the destination
  agent for a second time. Depending on the design of the
  SourceTransferStartExit, this could result in unexpected
  behaviour.
  

Problem conclusion

• To resolve this issue, MQ Managed File Transfer has been updated
  so that source agents only run SourceTransferStartExits before
  they send the initial transfer negotiation request message to a
  destination agent. If the managed transfer subsequently goes
  into a WaitingForDestinationCapacity state (because the
  destination agent is already participating in its maximum number
  of destination transfers), then the source agent will not re-run
  any SourceTransferStartExits prior to sending the subsequent
  transfer negotiation requests.
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
  Version    Maintenance Level
  v9.1 LTS   9.1.0.7
  v9.2 LTS   9.2.0.2
  
  The latest available MQ maintenance can be obtained from
  'WebSphere MQ Recommended Fixes'
  http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006037
  
  If the maintenance level is not yet available information on
  its planned availability can be found in 'WebSphere MQ
  Planned Maintenance Release Dates'
  http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006309
  ---------------------------------------------------------------
  

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:

Fix information

• Fixed component name

  IBM MQ MFT V9.1

• Fixed component ID

  5724H7272

Applicable component levels