IT35398: SourceTransferStartExits are run twice for the same managedtransfer following a network issue during negotiation

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_TRANSFER.
  
  Very occasionally, a network issue occurs which prevents the
  agent from being able to connect to its agent queue manager
  while performing transfer negotiation. As a result, the agent
  puts the managed transfer onto its backlog. When the agent
  attempts to negotiate the managed transfer again at a later
  time, the SourceTransferStartExit is run again. This causes the
  exit to return a CANCEL_TRANSFER ResultCode, which results in
  the managed transfer being marked as "Failed".
  

Local fix

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.
  
  Now, if a source agent detected a network issue while attempting
  to contact the destination agent as part of the transfer
  negotiation, it would put the managed transfer onto its backlog
  so that the negotiation could be retried later. However, when
  the agent picked up the managed transfer from its backlog, it
  would incorrectly re-run any SourceTransferStartExits before
  performing the negotiation. 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 now use the source transfer start exit
  results for a managed transfer, contained within the agent's
  state store, when
  determining whether any SourceTransferStartExits have already
  been run for that managed transfer. The source transfer start
  exits results are persisted in the state store as soon as the
  SourceTransferStartExits have been run, and before the transfer
  negotiation step begins.
  
  This means that if the managed transfer encounters a network
  issue during transfer negotiation, and is put onto the agent's
  backlog, then when the agent processes the managed transfer
  again, it detects that the SourceTransferStartExits have already
  been run, and so won't run them again before retrying the
  negotiation.
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
  Version    Maintenance Level
  v9.1 LTS   9.1.0.8
  v9.2 LTS   9.2.0.2
  v9.x CD    9.2.2
  
  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