Folks,
See the next writeup of where the AIX semaphores reside.
This is a response from Rob Abbott at Healthvision some time ago (maybe last year) and I went ahead and documented where the thread statistics were stored and why they went away when we rebooted our server.
Hope this helps out.
MSI statistics are stored in shared memory. The monitorShmemFile is simply a pointer to the shared memory.
Since the data are not stored on disk, it will not survive a failover to another physical machine. There is a shared memory segment that is reserved for statistics. I believe there is a separate segment for each site, though this may be platform dependent. This memory segment is not part of process memory – I suppose you could say it resides at the o/s level. Threads write statistics to this memory segment. Engine utilities such as hcimonitord and hcimsiutil, msiAttach, msiGetStatSample, msiTocEntry read from it. (I believe this list of tools that read from shared memory is complete – for example Network Monitor does *not* access shared memory directly, it talks to hcimonitord).
The memory segment is destroyed when the machine is shut down, so any data there is lost. Since this is all in memory it’s volatile storage.
Nothing is stored on disk, other than a pointer to this memory segment which resides in monitorShmemFile. On AIX you can see the shared memory segments and the semaphores used to manage locking of these segments by running the “ipcs” command.
Note: for information on the ‘ipcs’ command, use the manpage utility on your AIX server (if installed).
Note: enhancement request #12209 on 11/19/2008 was submitted to Healthvision to create a utility to offload and restore these statistics. Courtesy of Rob Abbott.
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