Adding Memory in OpenVMS 6.21H3

[Vimal Upreti]

Hi all,
I’m planning to upgrade memory of Alphaserver 4100 with OpenVMS 6.2-1H3 from 512MB to 2.5 GB. Any parameter has to be updated to get better performance of the System.
I think I have to run @swapfiles to increase the Swap & Page Files. How much should be their values?
Any other changes in SYSGEN/SYSMAN Parameters?

Thanks in advance.
Vimal

[Volker Halle]

Vimal,

as a first step, I would suggest to rely on running @SYS$UPDATE:AUTOGEN GETDATA SETPARAMS FEEDBACK to set up the system parameters after upgrading the memory configuration. Make sure to shut down the system with SAVE_FEEDBACK (before installing the additional memory), if you have not saved the feedback data otherwise before.

Note that performance will only increase by adding memory, if memory was a limiting factor before.

Make sure that there is enough disk space on your system disk or on the disks where your page/swap/dump files reside. Note that AUTOGEN (or @SWAPFILES) may not be able to increase the size of your page/swap/dump files, if the disk is too fragmented. These files can not use extension file headers.

You can test the suggested file size running @AUTOGEN GETDATA TESTFILES FEEDBACK

Volker.

[Ian Miller.]

you may not have to increase the page/swap files as their use is less likely when you have more memory. The crash dump file will have to be bigger. After the upgrade review your WSDEF, WSQUO, WSEXT limits for processes that could benifit from more memory. Also review WSMAX.
You may wish to increase MAXPROCESSCNT depending on why you are adding the memory (bigger processes or more processes or both).

[comarow]

Often when people make changes to their systems that require autogen, they think the change broke their system.

Actually, it was because they hadn't run autogen in a long time, and very often have made changes directly to sysgen. As someone earlier suggested, you might want to make sure your system can execute autogen

On an old system, take control of your page and swap file. Unless you are also going to increase their load, you will need less pagefile, but autogen will want to increase it. In addition, as someone pointed out, your system disk may be badly fragmented, and it will fail.

Adding the lines
pagefile=0
swapfile=0

can save your system.

Do a show mem/file and make sure you have plenty of free space. Ignore the reservable number, even if it is negative. It is theoretical only.

You may likely need a larger dump file.
Chances are you will want to make

Dumpstyle=1 ! selective dump
or
Dumpstyle=9 ! compressed selective dump

If you have not defragmented your system disk, even lettting autogen create a dumpfile can lead to a problem.

Before you shut down, SAVE YOUR FEEDBACK with a full load, so autogen can make decisions based on the full load.

Be very careful when you save your feedback, only do it when you've had a full load on a system. The system can use that full load of feedback after you add the memory.

While at 512 mb
@sys$update:autogen savparams

after adding memory

$sys$update:autogen getdata setparams feedback

Do NOT use SAVPARAMS after adding memory until you have had your full load.

Look for any hard coded valued in your
modparams.dat, and generally change them to a min_value

Example

WSMAX = 64000
chagne to
MIN_WSMAX=6400

Warming. It will increase WSMAX, and it will
increase PQL_MWSMAX

This means that you are likely to have a
PQL_WSMAX larger than a user's page file quota. When they run a sort or convert, it will fail. If users execute sorts or converts, increase their pagefile quota above WSMAX.


Adding memory can help relieve IO problems and other memory type issues. There's little reason with cheap memory available not to add memory.

As far as sizing your page and swap file,
do that depending on useage.
$show mem/file should have several hundred thousand free blocks.

Interestingly, if you type
agen$feedback.dat
it will show you the peak pagefile useage.

The best parameters to increase after adding memory are users working set quotas.
That's where you'll get bang for the buck,
if you have set MIN_ in modparams.dat

BTW, unlike a VAX, the system will immediately see the memory as soon as you reboot. There is an article you get get from support on adding memory called

Tuning an OpenVMS System After Adding/Removing Memory


Have fun.