AIX

Yes, good old shared memory is used by the traditional UNIX IPCs, including semaphores and queues. I am not sure why these have to be pinned. Pinning is usually for peripheral/I/O support or the paranoid.

You can do similar things without shared memory or pinning using mmap() and files. An area of a file can be mmap()'d by all related processes, no root required. The content is durable through boots, too!

Ahem, "pinned" is not "shared". It is just that most of the standard applications which use pinned memory (foremost Oracle DB) also use shared memory segments to a large extent. Therefore i took an "educated guess" that maybe the presence of pinned memory hints at such a software being used. Why they do it that way? Ask Oracle! I just administrate machines running their product.

I hope this helps.

bakunin

Guess I need to write a program to find out definitely what system calls are being used to share memory segments on AIX.
IIRC (if I recall correctly) - shmap()/mmap() - pins a file to memory. And misuse by applications can have a tremendous impact on memory management. And "way back when - AIX 4.1.4 and 4.1.5 if I recall, shmap()/mmap() were null operations on AIX (for POSIX they only need(ed) to be defined ("standards guy" might verify this) - i.e., there was/is no implementation definition. And why a null operation? Because AIX was already caching files in memory by default.
Note: currently (since a patch in AIX 4.2 or 4.3) expected shmap/mmap behavior is implemented in AIX - so also since "way back...".

Again, on AIX - the preferred tool for memory analysis is svmon.