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How to increase pagefile space?

Super Advisor

How to increase pagefile space?

Our VAx is starting to run out of pagefile space, we would like to increase the amount of pagefile space. What are the necessary steps I need to take. Thanks!
Robert Gezelter
Honored Contributor

Re: How to increase pagefile space?


The easiest way to correct this long term is to re-size the page file using SYS$UPDATE:SWAPFILES.COM.

You can also use the CREATE and INSTALL commands within the SYSGEN utility to install a secondary page file.

Running SWAPFILES.COM will require a reboot, adding a secondary page file DOES NOT require a reboot.

You will of course, need the appropriate privileges to do these operations.

I hope that the above is helpful.

- Bob Gezelter, http://www.rlgsc.com
Robert Gezelter
Honored Contributor

Re: How to increase pagefile space?


Note: If you create a secondary page file, you will need to add it to the startup command file (the easiest way to do this is by modifying SYS$MANAGER:SYSTARTUP_VMS.COM.

- Bob Gezelter, http://www.rlgsc.com
Andy Bustamante
Honored Contributor

Re: How to increase pagefile space?

The simple answer is to run


and increase the appropriate pagefile.

The problem with the easy answer is you need disk space, (contiguous disk space is better) and you want to prevent saturating a disk's I/O capabilities. Increased paging can lead to application slow downs which may not be acceptable to your user base.

You can add an additional page file to the system manually with appropriate values for disk and dir:

$ mcr sysgen create disk:[dir]pagefile2.sys /contig/size=xxx

$ mcr sysgen install disk:[dir]pagefile2.sys /pagefile

This second line needs to be added to your startup proceedure. Again you want to avoid having paging I/O conflict with your application. If you have the disk available this will spread out the I/O load.

Your third option is to add more memory to the system.

If you don't have time to do it right, when will you have time to do it over? Reach me at first_name + "." + last_name at sysmanager net
Ian Miller.
Honored Contributor

Re: How to increase pagefile space?

Miles, welcome to the itrc vms forum.
Purely Personal Opinion
Wim Van den Wyngaert
Honored Contributor

Re: How to increase pagefile space?


If you are still on 6.x, enlarge the current pagefile and reboot. Processes expanding their memory usage will not overflow to another pagefile without problems (they reserved memory that they think they will get while the memory is no longer there).

Karl Rohwedder
Honored Contributor

Re: How to increase pagefile space?

When you want to increase the primary pagefile, pls. note that a pagefile.sys can't habe extension file headers.

So when your systemdisk is quite fragmented, and you have enough free space, it may happen, that your pagefile is extended with lots of small extends and didn't reach the desired size (conitgous best try algorithm).

A better way is to check for the largest free extend (there a are some utilities floating around for this), add this to the current size and extend the pagefile accordingly. Repeat this steps as long as needed/possible.

regards Kalle
Peter Quodling
Trusted Contributor

Re: How to increase pagefile space?

And if you are fiddling with Pagefiles, a) minimize the size of the one on your system disk, and b) create a secondary on another disk, that has good i/o bandwidth, isn't full or heavily used. Taking the pressure off the system disk makes sense. I know of a number of big VMS configs that run multiple dedicated disks for page/swap.

Leave the Money on the Fridge.
Veli Körkkö
Trusted Contributor

Re: How to increase pagefile space?

First of all you should check SYSGEN parameters


as these determine maximum number of swap/pagefiles on system. Compare these to number of those existing (in use) swap/pagefiles
and raise if needed. (Needs editing of MODPARAMS, execution of AUTOGEN and reboot to change).

Now, I would recommend having pagefiles/swapfiles somewhere else than system disk assuming that you have such disk available.

Also I would recommend having all pagefiles equal size. Same for swapfiles also. e.q.

disk1:[dir]swapfile1.sys 400001 blocks
disk2:[dir]swapfile2.sys 400001 blocks
disk1:[dir]pagefile1.sys 800001 blocks
disk2:[dir]pagefile2.sys 800001 blocks

I would leave a SMALL pagefile or swapfile lurking around in system disk at all.

And if system seems to have swapped out processes (like processes in state LEFO, HIBO) I would indeed have swapfile(s) on system (and with large enough size)

Not that since this VAX, there is really no point creating page/swapfile larger than approx 1000000 blocks since

$ mc sysgen create dsa1:[000000]p.sys/size=1100000
%SYSGEN-I-CREATED, DSA1:[000000]P.SYS;1 created
$ mc sysgen install DSA1:[000000]P.SYS;/page
$ sho mem/files
System Memory Resources on 11-SEP-2005 09:46:17.56

Paging File Usage (pages): Free Reservable Total
USR:[SYSEXE]SWAPFILE.SYS;1 100000 100000 100000
USR:[SYSEXE]PAGEFILE.SYS;1 216123 122095 300000
USR:[000000]P.SYS;1 1048568 1048568 1048568
USR:[000000]P.SYS;1 51424 51424 51424

that file gets split to two "logical pagefiles" and that is no good.