Volume/Subvolume creation

[Kot]

Hi Group,

Whats the best way of creating a Volume/Subvolume on tandem with providing the required properties.

Can we use FUP for creating a Volume/Subvolume.

Thanks in Advanvce..

[Keith Dick]

I believe you have a basic misunderstanding.

Let's talk about subvolumes first. You probably think they are like Unix or Windows directories. They are not. A Unix or Windows directory can exist even when there are no files in it. A subvolume does not exist if there are no files "in" it. A subvolume is more like a portion of the file name than it is like a Unix or Windows directory.

A subvolume X is created when you create a file that has X as its subvolume name. Any command that creates a file and that accepts a full file name will create the subvolume if the subvolume is not already there. For example, the TACL command:

CREATE $VOL.X.FILE

creates a file on disk $VOL with the name X.FILE. Dividing the name into subvolume and filename allows you to easily group files that have some relationship into a subvolume, but the subvolume really has no existence independent of the files that use its name.

The VOLUME command allows you to specify the default volume and subvolume name that will be used to complete a filename if you write a filename that does not include the volume or subvolume part of the name. The VOLUME command does not create anything on disk. For example, these commands:

VOLUME $VOL.X
CREATE FILE

creates a file on disk $VOL with the name X.FILE, same as the command above did.

I hope that helps you understand how subvolumes work. In many cases, you can think of a subvolume as being the same as a Unix or Windows directory, but there are a few cases where you will be led astray if you think that way.


Now, about volumes. There are two kinds of volumes -- real, physical disks and logical disks, virtual disks or SMF disks (three names for the same thing).

In one sense, you do not create a real, physical disk with a software command -- it is a piece of hardware that exists on its own. You do use a software command to tell the system about a physical disk and give a name to it. The SCF utility is used to tell the system about a physical disk. The command is ADD DISK. Look in the manual "SCF Reference for the Storage Subsystem" to see the details of the ADD DISK command and all the other SCF commands that work on disks.

You *do* create a virtual disk with a software command -- it is entirely a software construct. A virtual disk uses space on one or more physical disks to store the files you put on a virtual disk. The SCF utility also is used to create virtual disks. The command also is ADD DISK, but the arguments to the command differ from those with physical disks. Before you create a logical disk, you must create the SMF storage manager and a storage pool for the virtual disk to use. All this is described in the manual "SCF Reference for the Storage Subsystem". There also is a manual "Storage Management Foundation User's Guide" that explains virtual disks.

Configuring physical disks and creating virtual disks are operator tasks that I believe cannot be done by ordinary users.

[Kot]

Thank you Keith for an elaborated explanation.It was very helpful.

Got my Query Clarified :-)

[Bill Honaker]

Just one comment to add to Keith's; there are Safeguard entities used to protect subvolumes. If you use Safeguard to protect or audit your files on disk, you should refer to the manuals.
Bill

[Rob Lesan]

Another comment to add to both Bill and Keith.

Securing subvolumes can be tricky! Restricting access to them (and the ability to create them) is even more complex.

If you need help with any of this, feel free to contact me (rob....@xypro.com).