In this context, I believe that the "in-use" and "not-in-use" references are referring to allocations which have been marked "not-in-use" using the DAIR interface. This interface is documented in TSO/E Programming Services topic 17.2.2.11 Marking Data Sets as Not in Use (Entry Code X'2C').
Basically, my understanding is that the DAIR interface is as old as the hills, and the concept of optimizing TSO performance by marking allocations "not in use" probably dates to OS/360 - but of course the TSO historians will correct me with the details. The two concepts - 1) marking an allocation "not in use" and reusing a "not in use" allocation, and 2) using the REUSE keyword on the ALLOC command, are two totally separate and distinct concepts. Another way to think about this is DAIR predates DYNALLOC. And, it used to be that Allocation was REALLY SLOW. So the DAIR service to mark allocations "not in use" was an attempt to optimize TSO, back in the olden days. Brian On Tue, 17 Jan 2006 08:04:49 -0700, Paul Gilmartin <[EMAIL PROTECTED]> wrote: >The description of DYNALLOC is frightening with in-use and not-in-use >allocations, and the possibility of reusing an existing allocation >rather than creating a new one. It states there is a performance gain >for reusing an existing allocation. Where? Can it bypass catalog >lookup or VTOC lookup? Does the SYSDSN ENQ remain in effect while an >allocation is not-in-use? If not, what happens if another job >deletes (and perhaps even recreates and catalogues) a data set >associated with a not-in-use allocation? Does the TSO FREE command >actually remove the allocation, or merely set the not-in-use flag? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
