PH51546: Managed File Transfer (MFT) agent ABENDs with a B37-04 condition while transferring to a sequential data set.

APAR status

• Closed as program error.

Error description

• An IBM MQ Managed File Transfer (MFT) for z/OS agent is acting
  as the destination agent for managed transfers. While trying to
  write data to a sequential data set, the agent ABENDs
  unexpectedly with a B37-04 condition.
  

Local fix

Problem summary

• ****************************************************************
  USERS AFFECTED:
  This issue affects users of:
  
  - IBM MQ 9.1 Managed File Transfer for z/OS
  - IBM MQ 9.2 Managed File Transfer for z/OS
  - IBM MQ 9.3 Managed File Transfer for z/OS
  
  who have MQ Managed File Transfer (MFT) destination agents
  running on z/OS that are writing data into sequential data sets.
  
  
  Platforms affected:
  z/OS
  
  ****************************************************************
  PROBLEM DESCRIPTION:
  MQ Managed File Transfer (MFT) agents running on z/OS use the
  JZOS Toolkit to access data sets. The toolkit itself acts as a
  thin layer between Java applications and the underlying z/OS
  Language Environment (LE) which interacts with the mainframe's
  file system - when the agent calls a method on a class provided
  by the toolkit, such as ZFile.write(byte[]), it delegates that
  call down to the LE for processing. Here is a simple diagram
  that shows this relationship:
  
  MQ Managed File Transfer agent on z/OS
      |-----> JZOS Toolkit
          |-----> Language Environment (LE)
              |-----> Data set
  
  
  Now, when the issue reported in this APAR occurred, the
  following sequence of events had taken place:
  
  - An MFT agent running on the mainframe had received a request
  for it to act as the destination agent for a managed transfer to
  a sequential data set.
  - In order to access the data set, the agent created a new JZOS
  ZFile object passing in an options string similar to the example
  below:
  
  "wb,recfm=FB,blksize=27840,lrecl=320,noseek"
  
  - When constructing the ZFile object, the JZOS Toolkit called
  the LE function fopen() passing in the options string.
  - The LE opened the data set using the specified options, and
  returned a handle to it to the JZOS toolkit.
  - JZOS stored the handle in the ZFile object, and then returned
  that object back to the agent.
  
  - After writing some data to the data set using the ZFile
  object, the agent then called the JZOS method
  com.ibm.jzos.ZFile.close().
  - This resulted in the JZOS Toolkit calling the LE function
  fclose().
  - While processing the fclose() function, the LE determined that
  there was some buffered data stored in control blocks which
  needed to be written to the data set.
  - However, the LE was unable to write the data because the
  sequential data set was out of extents.
  - Because the data set was not opened with the:
  
  "abend=recover"
  
  option specified, the LE generated an ABEND with a B37-04
  condition - this was the expected behaviour, as documented in
  the
  
  "fopen() and freopen() parameters"
  
  topic in the z/OS 2.x sections of the IBM Documentation site.
  The URI for this topic in the z/OS 2.3.0 section of the IBM
  Documentation site is
  https://www.ibm.com/docs/en/zos/2.3.0?topic=files-fopen-freopen-
  parameters.
  
  - As a result, the MFT agent process stopped unexpectedly.
  

Problem conclusion

• To resolve this issue, MQ Managed File Transfer agents running
  on z/OS have been updated so that:
  
  - If the agent is acting as the destination agent for a managed
  transfer
  - And it needs to write data to a data set
  
  then it will include the option:
  
  "abend=recover"
  
  when the data set is opened. This means that the Language
  Environment (LE) will try to handle any out of space conditions
  that might occur when writing data to the data set (such as a
  lack of extents) gracefully and return an error back to the JZOS
  Toolkit, which in turn will pass an exception back to the agent.
  
  As a result, the agent will mark managed transfers as "Failed"
  with supplementary information similar to the example shown
  below if an out of space condition occurs:
  
  BFGTR0072E: The transfer failed to complete due to the exception
  : <data set name>: BFGIO0069E: A write failed. The data set may
  be out of space fwrite() failed; EDC5065I A write system error
  was detected.; errno=65 errno2=0xc03e0002 last_op=151
  errorCode=0xb370004; EDC5065I A write system error was
  detected.; errno=65 errno2=0xc03e0002 last_op=151
  errorCode=0xb370004 abend(syscode=0xb37 rc=0x4)
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
  Version    Maintenance Level
  v9.1 LTS   9.1.0.15
  v9.2 LTS   9.2.0.10
  v9.3 LTS   9.3.0.5
  v9.x CD    9.3.3
  
  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 Z/OS

• Fixed component ID

  5655MF900

Applicable component levels