Hi, Tony,
Look here:
The last two manuals on that page will answer ALL of your questions about how TSO worked on SVS. :-)
Each TSO user, at LOGON time, is allocated a REGION, the size of which is of course controlled by their LOGON PROC. That region is a contiguous chunk of the total 16 MB virtual address space of SVS, but because it is TSO, the SVS supervisor ensures that this region is paged to the "TSO" reserved page space.
There is never a full region "roll-out" or "roll-in" like the swapping in MVT, because in MVT, you had a fixed number of pre-allocated "slots" for TSO users to run in, so they had to swap out that entire space, or all of it that you used, to make way for the next tSO user to get swapped in. In SVS, they just leave it to "demand paging" to steal any pages needed. Then, when it is "your turn" to get dispatched again, you will just demand page in any of your pages that were "stolen."
What you can see with SVS is that it is an evolutionary step towards MVS 2.0 and above, where TSO became an integral part of the OS, no longer "optional." The only "option" about TSO in MVS is whether or not you use it.
Hope that helps,
Mark
