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IC99372: A WEBSPHERE MQ FILE TRANSFER EDITION V7.0.4 MESSAGE-TO-FILE TRANSFER OVER SFTP FILE SERVER ENTERS RECOVERY

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APAR status

  • Closed as program error.

Error description

  • When performing a message-to-file transfer using the SFTP
    protocol to a file server, the transfer enters recovery and the
    SSH server log reports the following error:
    
    SSH_MSG_DISCONNECT: 2 Received data for nonexistent channel 0.
    
    This error message is also output in the trace logs by the
    WebSphere MQ File Transfer Edition protocol bridge agent when
    tracing for the agent has been enabled.
    
    The exception can occur multiple times during the transfer, and
    each time it results in the WebSphere MQ File Transfer Edition
    protocol bridge agent performing recovery processing on the
    transfer.
    

Local fix

  • Configure the WebSphere MQ File Transfer Edition agents such
    that they are able to transfer all the data for the final file
    within one transfer chunk.
    
    In order to do this, you need to know the maximum size of the
    file being transferred, which is the total size of the message
    data on the source queue.
    
    This is configured using three agent properties, which are
    multiplied together to determine the maximum chunk size:
    
      "agentChunkSize" defaulting to 262144 bytes (256 KB)
      "agentFrameSize" defaulting to 5
      "agentWindowSize" defaulting to 10
    
    These values multiplied together give you the upper JVM memory
    limit used for a specific transfer, which with the default
    values is 12.5 MB.
    
    
    If you increase these values (eg. change the "agentChunkSize"
    agent property) so that the multiplication of the three values
    gives a value which is greater than the transferred file size,
    then the system will circumvent the issue.
    

Problem summary

  • ****************************************************************
    USERS AFFECTED:
    This issue affects users of the WebSphere MQ File Transfer
    Edition protocol bridge agent who perform file transfers to or
    from file servers using the SFTP protocol.
    
    
    Platforms affected:
    MultiPlatform
    
    ****************************************************************
    PROBLEM SUMMARY:
    WebSphere MQ File Transfer Edition protocol bridge agents can
    perform file transfers to and from a file server using the SFTP
    protocol.
    
    When performing a file transfer to an SFTP file server, file
    data that arrived at the protocol bridge agent, and read off the
    agent's SYSTEM.FTE.DATA. queue, was queued internally and later
    processed by a thread dedicated to writing the file data to the
    file server.
    
    The first thread that was created to process the initial file
    data was responsible for establishing a connection to the SFTP
    file server and opening an OutputStream to the destination file
    to which the file data could be written. This thread then writes
    the queued file data to the OutputStream. Once all the data that
    has been received by the protocol bridge agent had been written
    and the internal queue became empty, the thread waited for a
    short period of time for more data to arrive. If no more data
    arrived within that period of time, for example because the
    WebSphere MQ File Transfer Edition source agent is under load,
    the thread processing the queue was terminated.
    
    When more file data was then later received by the WebSphere MQ
    File Transfer Edition protocol bridge agent, sent from the
    WebSphere MQ File Transfer Edition source agent for the
    transfer, a new thread was started to process the file data.
    This new thread, used the cached connection and OutputStream
    that was previously created by the first thread. The fact that
    this new thread reused the OutputStream to write the new file
    data caused the SFTP file server to throw the exception outlined
    in the Problem Description section of this APAR. This resulted
    in the agent closing the connection to the SFTP file server, put
    the transfer into recovery and attempt to restart the transfer
    from the last checkpoint.
    
    The same issue can occur when transferring a file from an SFTP
    file server as the InputStream could have been shared across
    multiple threads.
    

Problem conclusion

  • The WebSphere MQ File Transfer Edition protocol bridge agent
    code has been updated such that the same thread is used when
    writing and reading file data on a file server when using the
    SFTP protocol.
    
    ---------------------------------------------------------------
    The fix is targeted for delivery in the following PTFs:
    
    Version    Maintenance Level
    v7.0       7.0.4.5
    v7.5       7.5.0.5
    
    The latest available 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

    IC99372

  • Reported component name

    WMQ FILE TRANSF

  • Reported component ID

    5724R1000

  • Reported release

    704

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2014-02-14

  • Closed date

    2014-04-29

  • Last modified date

    2014-04-29

  • 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

    WMQ FILE TRANSF

  • Fixed component ID

    5724R1000

Applicable component levels

  • R704 PSY

       UP

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Document Information

Modified date:
29 April 2014