On Fri, 10 Mar 2023 at 13:31, Mark Waterbury <mark.s.waterbury@...> wrote:
Hi, Tony,
In SVS, it specifically prohibits you from running TSO in a V=R region,
Yeah - I thought that one was unlikely for a few reasons.
Also, they got rid of "swapping" in the sense of those swap data sets used in OS/360 MVT.
Instead, what you do is to reserve a certain percentage of the total paging space for use by
TSO. When TSO is inactive, of course batch can also use that page space. Then, when a
TSO user goes into a "long wait" their pages are eligible to be "stolen" in the usual way by
the paging subsystem, to make room for other pages needed for other TSO users, etc.
Interesting... I'm still not getting this entirely, though. In MVT
TSO, for a given TSO region, all users shared the same address range,
and each user's space was swapped in and out. So necessarily there
were multiple unrelated chunks of storage in the same swap dataset
with the same main storage address range. I have no recollection of
what the swap datasets looked like, but I don't think they were
page-oriented, and they must have always swapped the entirety of
GETMAINed storage (because there were no change/reference bits to know
if pages were in use).
If the swap datasets are gone in SVS, then it sounds as though there
must have been some private interface to the paging system to be able
to write out multiple pages with the same address range, i.e. Multiple
Virtual Storages... :-)
Hmmm... Does SVS have VIO? I think that came only with MVS, but it
sounds like something that would require a similar interface.
Also, you could put certain TSO commands, such as EDIT, in the LPA, so they would be
shared by all TSO users.
I think even MVT allowed for that. Wait - does MVT even have an LPA?
There is JPA, but that's not global.
Hope that helps,
It does - thanks.
Tony H.
