It's beginning to sound like z/VSE is an improvement in several ways on z/OS.  
I wrote a production job recently that updates a dataset pretty much anyone can 
View (a list of current Top-Secret ACIDs to see what so-and-so's ACID is, or 
who belongs to ACID such-and-such).  The update has to read a largish-security 
database.  The last step is a SORT that takes less than a second - but I had to 
put it in a separate job, and have it triggered by the previous job, because 
otherwise the dataset would be unavailable for Viewing by any user while the 
long job was running.

---
Bob Bridges, robhbrid...@gmail.com, cell 336 382-7313

/* There is no harm in being sometimes wrong — especially if one is promptly 
found out.  -John Maynard Keynes, Essays in Biography (1933) */


-----Original Message-----
From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf 
Of Tony Thigpen
Sent: Monday, March 30, 2020 11:38

Actually, there is no 'allocation' of a file by z/VSE during the JCL 
processing. The file is only 'allocated' once it is opened and 
'unalocated' once the program closes the file.

For instance, if you have a 5 hour program, that just needs to update a 
'totals' VSAM file at the end of the 5 hours, as long as the program 
does not open the file until it needs the file, any other program can 
use, including updating, the file until that time.

So, basically, you 'own' the file only while you have it opened.

One ramification is that you can't create a file simply by having in the 
jcl, like in z/OS. You have to open it to create it.

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