IBM Support

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

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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 number

    IT35398

  • Reported component name

    IBM MQ MFT V9.1

  • Reported component ID

    5724H7272

  • Reported release

    910

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2021-01-04

  • Closed date

    2021-01-22

  • Last modified date

    2021-01-22

  • 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

[{"Line of Business":{"code":"LOB36","label":"IBM Automation"},"Business Unit":{"code":"BU053","label":"Cloud & Data Platform"},"Product":{"code":"SSYHRD","label":"IBM MQ"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"910"}]

Document Information

Modified date:
23 January 2021