BMP
Batch message processing: an IMS batch program that runs alongside online transactions and uses the same live databases.
Also written batch message processing, BMP region, CHKP, XRST
A BMP, or batch message processing program, is a batch job that runs under the control of the online IMS system. It can read and update the same databases that online transactions are using, at the same time.
That is the main difference from a DL/I batch job, which opens the databases on its own and needs them to be unavailable to online work while it runs. A BMP lets batch and online work share data, which matters for systems that must stay open most of the day.
A BMP must take checkpoints regularly with the CHKP call. A checkpoint commits the changes made so far and releases the locks held on them, so online transactions are not kept waiting. It also records a position that the job can restart from.
If a BMP fails, IMS backs out the changes made since the last checkpoint. The job can then be restarted with the XRST call, which continues from that checkpoint instead of from the beginning. How often to checkpoint is a balance: more often keeps locks short, less often runs a little faster.
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- IMSAn older IBM transaction manager and hierarchical database, still running some of the highest-volume systems in the world.
- Batch processingRunning work in bulk, without anyone watching, usually on a schedule. The overnight run that settles a day of transactions.
- Commit and rollbackMaking a set of changes permanent together, or undoing them together, so a transaction never half-happens.
- DL/IData Language/I: the set of calls a program uses to read and update an IMS database.
- Batch windowThe period, usually overnight, in which batch work has to finish before the business needs the systems back.