Oracle Instances and real memory consumption on Linux and Solaris

There’s a way to know the REAL memory usage by Oracle Instance, including all connecting processes and using the shell rather than a connection to oracle?

The short answer is “I think so” 🙂

Summing up RSS column from ps output, is not reliable because Linux uses a copy-on-write on process forks and also doesn’t take into account correctly the shared memory and other shared allocations.

I’ve come across this post on Pythian’s Blog from Marc Billette.

While it seems good I’ve had discording results depending on platform and release.

Instead, I’ve tried to create a shell snippet that always uses pmap but works differently and SEEMS to work correctly on Linux ans Solaris.

Basically, using the pmap script I get a lot of information about the different memory areas allocated to the process:


Initially I’ve tried to decode correctly the different kinds of memory the same way other scripts I’ve found online do:

but finally the ADDRESS is the same from different processes when the memory area is shared, so my script now just get a unique line for each address and sums up the memory size (not the rss one!):

This should give the total virtual memory allocated by the different Oracle instances.

The results I get are plausible both on Linux and Solaris.


If you find any error let me know and I’ll fix the script!