What are vmmX* files on Cognos temp dir for?

[gabbagabba]

At my company we have a Cognos BI 10.1 environment running on IBM AIX, set up across three clustered servers. Our temporary drive space is running low, and poking around the temporary directory we found a large number of extremely huge vmmX* files, most of them around the ~500 MB and some of them reaching the 2 GB of size, most of them dating back from 2012. I found this official tech note explaining what one would expect to find at Cognos's temp dir but nothing about these files. I couldn't find anything about AIX's VMM process using temporary files either.

Since these files are seriously bloating our Cognos installation directory a lot, is it OK if we delete these files?

[MMcBride]

I do not have an answer to your question, I do not know what those files are for.

However that being said my basic rule of thumb is anything in the Temp directory is free game for deletion.
I also run on AIX and I cleared out 17 GB of vmmX files and see no detrimental issues on my server.

I believe these are files created for intermediary results and since AIX tends to drop threads at random intervals... My most common errors are async communication errors that not even IBM can clear up for me I am guessing these files are created and are not getting cleaned up when a report fails - you may not even notice an issue and simply rerunning the report solves it - but the intermediary are still there.

This is especially true if you use Report Studio against Transformer cubes - I have seen some 20GB temp files created for a 4MB report due to the way Transformer handles cross dimensional analysis...

Anyway this is all just theory on my part - I have no idea what the vmmX files are for - but I keep mine cleaned up and haven't had any problems.
I usually clear out most of my Temp folder whenever I am restarting the services just out of habit.