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Operating System - Tru64 Unix
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vm-mapentries and Tru64 51.B

vm-mapentries and Tru64 51.B

An Oracle consultant recommended to tune the vm-mapentries kernel parameter.

We are running Tru64 5.1B.

I find only valid references to this parameter in older Tru64 versions, like 4.0F, for example.

The only reference in the 5.1B documentation is within the man pages of the "dlopen" call:

"The maximum number of shared libraries that can be loaded simultaneously by a single process is approximately 60. This limit can be raised by reconfiguring the kernel's vm-mapentries parameter. This parameter should be set to at least three times the desired maximum number of shared libraries that can be loaded by a process."

Is this parameter not anymore needed in version 5.1B or replaced by another kernel parameter?

Hein van den Heuvel
Honored Contributor

Re: vm-mapentries and Tru64 51.B

This tuneable is retired.

Best I know this was not a performance tuneable, but a resource one.
That is, setting it higher than needed will not speed up anything, it will just waste memory.
And setting is lower than needed will break the application, so you will know real soon when it is too low.

You want to ask your Oracle consultant why / how you need to change this. What measurement / observation triggered the suggestion. What goal from the change.
Or... most likely... and not unreasonably... was he/she simply using a old check list. He/She better have a decent reply and not handwave nor bulldozer the issue otherwise he/she stands to loose a lot of credibility in my book.


Re: vm-mapentries and Tru64 51.B

Thanks. It was pointed out to me that there is an Oracle document 169706.1 (Oracle RDBMS on AIX, HP-UX, Solaris,Tru64,Linux,MacOSX: Versions, Sizes, Requirements Quick Reference) which refers to modification of this parameter. It lists the requirements for the Tru64 versions 4.0D-G, 5.0, 5.0a, 5.1, 5.1a, 5.1b(EV5.6 processor or higher) and the Oracle version 8.1.7. Without distinguishing between the different Tru64 OS version, the document says to set the kernel parameter vm-mapentries to 1024. I guess the problem is keeping documentation short in quick references. I will close this thread in one or two days.

Re: vm-mapentries and Tru64 51.B