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What are UIC Groups 300-377 Reserved For?

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Homer Shoemaker
Frequent Advisor

What are UIC Groups 300-377 Reserved For?

This is my first post in this forum, but certainly not the first time I've used it. So I wanted to start out by thanking the many people who've answered my questions in the past without even knowing it. You guys are good!

We have a DS20 which is used for an application which consists of a few hundred COBOL executables and several hundred data files. The first versions of this application were written between and 1986 and they ran on a MicroVax. The application assumes all users will be on terminals and be logged out when they exit the application. We don't use it that way anymore. All users, by convention I assume, were put in UIC group 300. And I've just been continuing in that convention - not wanting to break anything.

Now my question.

I noticed from help in UAF "Digital reserves group 1 and groups 300-377 for its own use."

Why is that?

I want to put some groups of users in different UIC groups now, and I'd be more comfortable doing that if I knew whether or not I was already violating some important restriction - or relying on some property of a "reserved" group.

The OVMS version on our production server is Version V7.1-2

(Btw, we have two new rx2660's w/ 8.3 on order. I'm very excited!)
The Brit
Honored Contributor

Re: What are UIC Groups 300-377 Reserved For?

I cant say that this is absolutely gospel, but here is my theory based on an empirical examination of my own UAF file.

Looking at all accounts between Group 300 and 377 I see,


Note: No user accounts, all are either layered products or 3rd party products. Based on this I would conclude that these are reserved so that 3rd Party and Layered products can be installed using a hard-coded UIC Group number, without risking a conflict.

Just my 2c's worth.

Honored Contributor

Re: What are UIC Groups 300-377 Reserved For?

[1,*] is used for the username SYSTEM and brethern (SYSTEST, FIELD, etc) - [376,*] is used by DECnet for its collection of usernames that are associated with specific TASK servers. The remainder of the 300-377 range is used by a usernames belonging to a variety of VMS layered product servers. Basically, VMS arbitrarily reserved a collection of UICs to make it easier to create usernames with unique UICs when some layered product requires it.
Jan van den Ende
Honored Contributor

Re: What are UIC Groups 300-377 Reserved For?


to begin with:

WELCOME to the VMS forum!

Yes, group 1 is defenitely dedicated to VMS itself.
(and I always consider all UIC groups beow )SYSGENs) MAXSYSGROUP as such).
Groups 300 - 377 are the default UIC groups for several layered an d 3rd-party products.
And in this rather loose description also lies its freedom.
AFAIK, installing a product with an associated username probes if its default group is still unoccupied, and only then uses it.
Many (all?) also offer the installer to NOT accept that value.

In short, VMS tries to prevent collisions.

Really, the only danger I am am aware of, is a system manager that assigns new users to groups that already hold such "function-bound" account(s).
And yes, I have had the "pleasure" to disentangle one such mess. :-(

Better just play safe: There are enough groups available so that you can easily honor those reservings.



Have one on me.

Don't rust yours pelled jacker to fine doll missed aches.
Homer Shoemaker
Frequent Advisor

Re: What are UIC Groups 300-377 Reserved For?

Thank you, all.

Homer Shoemaker
Frequent Advisor

Re: What are UIC Groups 300-377 Reserved For?

I will create the new groups in the 4xx range.