What is Media ID mean when backups written to Disk means

[nasahasha]

When I look for backup id's in GUI catalog, Backups written to disk have media ID's @aaaax or @aaaav etc.,

Whats this media ID, and when is it assigned?

Does each disk pool or Disk stu have unique media id? Is this media ID static?

[RiaanBadenhorst · Accepted solution]

It is the ID of the disk pool. Each pool created will have on such as that.

[Nicolai · Accepted solution]

From 

http://www.symantec.com/docs/TECH154543

For all other disk based storage units and storage pools, a relative ID is assigned for each storage unit upon creation.

This Media ID is formatted with an asperant ("@") followed by a "one-up"  lettering system.  The first disk storage unit (including Basic Disk)  created is assigned "@aaaaa", the second "@aaaab", and so forth.  Once all the lower case letters have been assigned, the pattern repeats with the upper case letters, so after one pass through the next assignment would be "@aaaaA".