MPE/iX 5.5 Operating System Limits

The VSOD contains one entry for every transient object on the system. Transient objects
are defined as objects that are required during the life of a process, that have disc space
allocated on their behalf, and are released when the process terminates. The
VSOD/GUFD table contains one entry for every permanent object (ie. file) that is
mapped in (opened) or that has recently been mapped in (on the LRU list). Refer to the
discussions on the VSOD and VSOD/GUFD tables for more details.
The total number of objects that can be mapped in at any given time is 490637, which is
the sum of the maximum number of objects that can be defined in the VSOD and
VSOD/GUFD.
(5) VPN cache table - KSO049
Each VPN cache entry corresponds to pages of an extent that are currently in memory (or
ready to be mapped in/out of memory), hence the VPN cache table indirectly related to
the memory manament's PDIR table and the VSM extend B tree table. Entries are
"added" (locked in) when pages of an extent are mapped in memory and they are
"deleted" (unlocked) when pages of an extent are mapped out of memory. The number of
entries per open file depend on the pattern of access to the file. The VPN cache table size
does not directly limit the number of open files, but does limit the total number of pages
from all these file that can be simultaneously present in memory.
(6) VPN ar cache table - KSO051
As VPN CACHE table keeps track of pages that are curently in memrory or in motion in
for the pages with fixed access rights. The VPN AR CACHE TABLE provides the same
function but for pages with variable access rights pages. The two tables have the same
size and are managed the same way.
(7) VSOD table - KSO053
Every object in the system requires an entry in either the VSOD or VSOD GUFD table
(with the exception of certain resident objects that reside in the Disabled Expandable