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sysdef versus kctune

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Super Advisor

sysdef versus kctune

Hi All!


I come across a situation where by I was told by the application vendor that I need to change the value of maxdsiz_64bit to the value of 1048576, but when I run the following command:

kctune | grep maxd
maxdsiz                      2147483648  2147483648  Immed
maxdsiz_64bit                2147483648  2147483648  Immed

but when I use other command, I see something different:

sysdef | grep maxdsiz_64bit
maxdsiz_64bit            524288          -        256-1048576    Pages   -

So now I am confused , what is the real value of maxdsiz_64bit!!


I am running hp-ux 11.31 v3 on ia64 hp server BL860c server.

Please can someone help?

Patrick Wallek
Honored Contributor

Re: sysdef versus kctune

Both values are correct.


The output of kctune is shown in BYTES, so the value is 2,147,483,648 bytes / 2,087,152 KB / 2,048 MB / 2 GB.


The output from sysdef is shown in the number of memory pages (notice the word PAGES at the far right of the output), where a page is 4096 bytes.  So 524,288 pages times 4,096 bytes per page = 2,147,483,648 bytes or 2 GB.

Super Advisor

Re: sysdef versus kctune

Ok, thanks a lot, now to set it to 1048576 pages what sysntax shoud I use?  Please

Patrick Wallek
Honored Contributor

Re: sysdef versus kctune

1,048,576 pages = 4,294,967,296 byes (4 GB).


To set that value, use kctune.


# kctune maxdsiz_64bit=4294967296


Answer yes to the question about updating the automatic backup configuration.



Bill Hassell
Honored Contributor

Re: sysdef versus kctune

sysdef is deprecated for use in 11.31. Check the man page for sysdef at the bottom:

Note: sysdef will not be supported in future releases of HP-UX (refer
to WARNINGS section below). So users are advised to use the
kctune(1M) utility which provides additional information on kernel
tunable parameters.
sysdef is provided for compatibility purposes only and is no longer maintained since being marked for obsolescence in a future HP-UX release. The output from sysdef is known to be incorrect when reporting values for some tunable parameters such as msgmap, sema, and shmem.

The use of pages for kernel parameters has been quite confusing for many years.

Bill Hassell, sysadmin