John,

lots of good questions.
FWIW, we are currently underway to refresh the system limits
documents on Jazz (and hope to put it on ITRC, too, once it is
ready).

> Question 1:
> How many processes can simultaneously have an IMAGE database open?

Can't tell, what I know is that if you use User Logging with
Image, then you are definitely limited to 1140. The latter
is going to be increased with MPE/iX 7.5.

> Question 2:
> How many processes can simultaneously have a file open, or stated another
> way, on a system-wide basis, how many simultaneous opens of a single file
> are permitted (if there are restrictions for file types like Msg or access
> modes like GMULTI, etc. please specify)?

Theoretically there is no limit on how many processes can
share access to the same open file, in MPE/iX the internal
structures for keeping track of the accessors are linked
lists (with entries coming from large tables).

Practically speaking some structures maintain open counters
which are 16 bit large, so at 65,535 we would max out, but
we do not support that many processes anyway (7.0 Exp 1
can have 16k pins with BIGPIN).

http://jazz.external.hp.com/papers/limits/os_limits.html

has some info on MSG files, CM files, and MULTI/GMULTI
which AFAIK is still all correct.

> Question 3:
> How many files can a single process simultaneously have open?

1024.  7.5 is planned to increase that to 4096.


HTH,
Goetz.

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