>I'd use a semaphore.
>something like,
>when user requests datasets,
>inspect the semaphore file to see what is available,
>if dataset available create an audit line with UniqueID (sys(2015)),User,Batch,RecordRange,timestamp.
>When user finishes, remove audit line [or move it or mark it ignore].
>
>Then have code that looks for stale audit lines to prevent bogus lockouts.

How do you handle abnormal situations such as unproper computer shut down?