DSXchange

If a job aborts it is required eighter to reset it or compile it in order to rerun the job, why is this required, what happens when a job is reset which makes it eligible for re-run?

DataStage is designed so that when a job aborts it cannot be re-run again until it is reset. This is intentional so that a job cannot just continue to abort on subsequent runs without any noticing that it doesn't work. The "reset" of a job does nnot perform more than changing a status flag on the job, there is no cleanup or similar actiity involved.

As well as what Arnd said, resetting a job will roll back any uncommitted transactions, disconnect from data sources, close files and hashed files, and generally return the job to the state it was in prior to the last run request (as nearly as possible - transactions already committed remain committed). It also changes the job's status to "has been reset" if successful and, where relevant, moves any unlogged messages from the &PH& directory into the job log.

And as well, anything with a 'Backup' option like hashed or sequential files will have their backup restored, in essence resetting them back to their original state as well.