Finding the DL/I batch checkpoint ID

When an application program issues an IMS CHKP call, IMS sends the checkpoint ID to the z/OS® console and the SYSOUT listing in message DFS0540I.

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IMS also records the checkpoint ID in the type X'41' IMS log record. Symbolic CHKP calls also create one or more type X'18' records on the IMS log. XRST uses the type X'18' log records to reposition DL/I databases and return information to the application program.

During the commit process the application program checkpoint ID is passed to Db2. If a failure occurs during the commit process, creating an indoubt work unit, Db2 remembers the checkpoint ID. You can use the following techniques to find the last checkpoint ID:

  • Look at the SYSOUT listing for the job step to find message DFS0540I, which contains the checkpoint IDs that are issued. Use the last listed checkpoint ID.
  • Look at the z/OS console log to find message DFS0540I that contains the checkpoint ID that is issued for this batch program. Use the last listed checkpoint ID.
  • Submit the IMS Batch Backout utility to back out the DL/I databases to the last (default) checkpoint ID. When the batch backout finishes, message DFS395I provides the last valid IMS checkpoint ID. Use this checkpoint ID on restart.
  • When restarting Db2, issue the command -DISPLAY THREAD(*) TYPE(INDOUBT) to obtain a possible indoubt unit of work (connection name and checkpoint ID). If you restarted the application program from this checkpoint ID, the program could work because the checkpoint is recorded on the IMS log; however, the program could fail with an IMS user abend U102 because IMS did not finish logging the information before the failure. In that case, restart the application program from the previous checkpoint ID.
Db2 performs one of two actions automatically when restarted, if the failure occurs outside the indoubt period: it either backs out the work unit to the prior checkpoint, or it commits the data without any assistance. If the operator then issues the following command, no work unit information is displayed: 
-DISPLAY THREAD(*) TYPE(INDOUBT)