Anne & Lynn Wheeler
2006-09-13 05:48:12 UTC
That's compatibility. I'd imagine the "old way" with saveseg would
still create the spool file. If the named DCSS is not on the disks
that CP has accessed, CP would find the one on spool. But if you would
DCSSBKUP the file and store the file on the CP disk, it would find it
there first. We had a similar approach to phase out the override file.
The spool file is not flattened out either. When a userid issues a
diag64 against a yet unused DCSS, CP will need to walk the map in the
warmstart area and build segment and page tables to map the blocks. I
don't think walking the hyperblocks of a CMS file system is any
harder.
the real, original "old way" was with cms & cp supporting cms page mappedstill create the spool file. If the named DCSS is not on the disks
that CP has accessed, CP would find the one on spool. But if you would
DCSSBKUP the file and store the file on the CP disk, it would find it
there first. We had a similar approach to phase out the override file.
The spool file is not flattened out either. When a userid issues a
diag64 against a yet unused DCSS, CP will need to walk the map in the
warmstart area and build segment and page tables to map the blocks. I
don't think walking the hyperblocks of a CMS file system is any
harder.
filesystem ... that I had originally done on cp67 and then ported to
vm370. with page mapped filesystem ... then it was straight forward to
have all sort of shared segment feature/function mapped directly to
the stuff in cms filesystem.
they decided to pickup a very small piece of the cms & cp changes for
vm370 release3 and call it DCSS ... lots of past posts with much more
detailed description
http://www.garlic.com/~lynn/subtopic.html#mmap
one of the tricks was an added enhancement that i had done for
location free code ... so memory images could be mapped from
filesystem to arbitrary (possibly shared segment) virtual
addresses. lots of past posts discussing some of the issues
http://www.garlic.com/~lynn/subtopic.html#adcon
later i did an enhancement for the spool file system to operate
similarly ... i needed to speed up the spool system by minimum of
factor of 10 times for VNET participation in HSDT backbone
http://www.garlic.com/~lynn/subnetwork.html#hsdt
recent posts discussing spool file system rewrite
http://www.garlic.com/~lynn/2006e.html#36 The Pankian Metaphor
http://www.garlic.com/~lynn/2006o.html#64 The Fate of VM - was: Baby MVS???
http://www.garlic.com/~lynn/2006p.html#10 What part of Z/OS is the OS?