On Dec 10, 10:57am, SIMPKINS, Terry wrote:
> Subject: number of groups
> I know there must be a limit to the number of groups that can be in any one
> account. Does anyone know what the limit is?  or Where I can find it?
>
> Also, is there a maximum number of files that can be in a group or account?
>
> It there a maximum number of users in an account, or that can be "homed" to
> a given group?
>
> What is the current maximum number of datasets in a TurboImage database (I
> ought to remember that one, but I don't)?
>
> Terry Simpkins
> (preparing to build the "mother of all accounts")
>-- End of excerpt from SIMPKINS, Terry

Very good questions! I believe there was a communicator article discussing this
issue for 5.0 (push or pull I do not remember).

On MPE V, directories used to be stored as b-tree structures. However, MPE XL
(and MPE/iX) have always stored the root, account and group directories as
sorted files. Since these directories are files, they have a theoretical limit
of 4Gb of file space to store directory entries. !!!!HOWEVER!!!!, other system
limits will form practical limits way before you reach anything like this
theoretical 4Gb size.

Determining a practical limit (like most system limits) is an art as much as a
science. The current major gating factor for directories is the fact that
directory contents are attached to transaction management, and there is a limit
on the size of the transaction management system buffer. The more data that you
try to log, the more you increase the chance of having a stalled transaction
that will result in a system abort. Therefore, the smaller your directories,
the safer you are.

As a general rule of thumb, directory sizes of 1Mb or less should be highly
unlikely to cause any type of trouble. Now to translate this into the number of
entries per directory, you have to know the entry size. To keep things
interesting, the root, accounts, groups, and HFS directories all have different
record sizes. This is because they each have to store different types of
information in addition to the name and address of a file, such as accounting
information, security information, and so on. Also, note that the directory
entry size for a given directory type is constant, regardless of the type of
object that the entry points to. So, an account directory entry will be 180
bytes large, whether it points to a group, an HFS directory, or a file.

The following table gives the record sizes for each directory type:

        root           132 bytes          (~7,943 entries/Mb)
        accounts       180 bytes          (~5,825 entries/Mb)
        groups          40 bytes          (~26,214 entries/Mb)
        hfsdirs         96 bytes average  (~10,922 entries/Mb)

Now if you have a directory which exceeds these sizes, it's not the end of the
world. The way you use the files, your system load, the phase of the moon and
many other attributes will conspire to determine how likely large directory
sizes are to cause your system to abort. I would suggest, however, not to let
your directories ever exceed 3Mb.

Leaving the world of files and addressing the world of users, prior to MPE/iX
5.0 users used to be stored in a hidden directory associated with each account.
However, since 5.0 all users have been stored in a system-wide user "data base"
called HPUID.PUB.SYS. This file has a limit of 10,000 entries which implies
that 10,000 different users can be defined on a given system. There are no per
account limits, and no limit on how many of these users can be "homed" to a
single group.

I wish I could help with the dataset question, but I'll leave that to someone
who actually knows.

Hope this helps,
Craig

--
Craig Fairchild

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