Overview of units of work (UOWs)

The IMS online system uses a unit of work (UOW) concept to identify each application scheduling uniquely.

The identifier is 16 bytes (hexadecimal) and has the following format:

Bytes 0-3

The IMSID of the system.

Bytes 4-7

Blanks.

Bytes 8-11

The origin application sequence number (OASN) for the event. This number is set to zero when the online IMS system is cold-started and is incremented by one each time an application (the transaction or the BMP) is scheduled.

Bytes 12-15

The syncpoint number. The syncpoint number is set to zero during scheduling and increments each time the application is involved in the syncpoint process. The application is involved in the syncpoint process during application checkpoint processing, processing for the DL/I SYNC call, application termination if database updates or communication messages occurred, and when a GU to the I/O PCB is issued.

The OCREATE function requires the unit of work OASN to be supplied as part of the BMP execution selection criteria. This is necessary to prevent selection of database change records for a parallel scheduled program specification block (PSB). The OASN appears on the Listing of BMP Start/Stop Records Report generated by the FIND function. See the figure in Use-of-the-Find-Online-BMP-Executions-function for an example.

Note

The FIND function is used to obtain the executions for the desired PSB and return the OASN and syncpoint number for the UOW associated with each PSB execution. If the BMP issued checkpoints, the syncpoint number in the UOW when the BMP accounting record is written will be greater than 1.

Related topic

Using-the-BCF-Log-utility


 

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