Changing SYSGEN parameters without using sysgen

[Piet Timmers_1]

Hello everybody,

Question:

Is it possible, or is there a tool, to change sysgen parameters without using sysgen.

We use infoserver software to create disk images. We have images with OpenVMS 7.2, 7.3-2 and so on. And now we want to change a sysgen parameter on all these images. The "normal" way is to use the correct OpenVMS version, mount the image and use sysgen to adjust the parameter. But we want a faster way. Is this possible?

Thanks.

Piet

[Volker Halle]

Piet,

the sysgen parameters are stored in binary format in ALPHAVMSSYS.PAR (or VAXVMSSYS.PAR) on the system disk in the specific root of the system.

If you DUMP the file, you can certainly guess about the layout and then change the file contents with PATCH...

Volker.

[Piet Timmers_1]

Volker,

We have made a dump but we are looking for a more save way...?

(I now the most save way is to use MODPARAMS or SYSGEN)

Piet

[Volker Halle]

Piet,

what's safer than PATCH - once you know what you're doing ;-)

If it's a parameter, which relates to other parameter values, you should run @AUTOGEN anyway. If it's just a simple parameter value change not related to any other parameter, finding the parameter name with DUMP and locating the parameter value in the next couple of bytes is pretty straightforward. You can verify the binary value found in the file against the value found in the latest SETPARAMS.DAT file in that root.

I cannot think of any other 'supported' method except using SYSGEN.

Volker.

[Piet Timmers_1]

Volker,

We are not looking for a "supported" method, we do not think there is one other than using sysgen.

But when using dump and patch, you need to find out where to find the values in every version off OpenVMS we use. A special written tool thould be much easier.

Greetings,

Piet

[Volker Halle]

Piet,

the DISKBLOCK tool comes to mind (see OpenVMS Freeware CD):

$ MC DISKBLOCK
DISKBLOCK> select/file sys$system:alphavmssys.par
DISKBLOCK> sea/string="GBLSECTIONS"
%DSKB-I-SEARCHING, Searching blocks 1 to 21 for STRING "GBLSECTIONS" at 14:29:30
%DSKB-I-FOUND, STRING "GBLSECTIONS" Block: 1. Offset: 73 (%X049)

then
DISKBLOCK> DUMP
DISKBLOCK> EXAMINE ...
DISKBLOCK> DEPOSIT ...
DISKBLOCK> REWRITE

Volker.

[Hoff]

Going around SYSMAN is not without some risk. (SYSMAN applies various blade-guards to the chosen settings, for instance. With PATCH, the results might not be bootable.)

I'd probably make the parameter changes in MODPARAMS.DAT and trigger the AUTOGEN reboot cycle during the boot; I'd use the same basic mechanism that OpenVMS uses for this purpose. Either load your own MODPARAMS, or append your settings, or use the included-file syntax.

There are other data files containing system parameters around, and that feed calculations into the whole process.

You would be able to use this same MODPARAMS scheme to customize specific installations, and to manage future parameter changes.

I've had experience with these fast-load configurations, and the Host-based InfoServer makes this really nice. Where it gets a little weird is with the corner cases, such as the GPT disks, or (as you've discovered) with site-local system parameters.