When you request a restore, the default is to use a maximum
of one session.
Additional restore sessions are based on:
- resourceutilization value
- how many tapes on which the requested data is stored
- how many tape drives are available
- the maximum number of mount points that are allowed for the node
Note: - If all of the files are on disk, only one session is used. There
is no multi-session for a pure disk storage pool restore. However,
if you are performing a restore in which the files are on 4 tapes
and others are on disk, you could use up to 5 sessions during the restore.
- The Tivoli® Storage Manager server
can set the maximum number of mount points a node can use on the server by
using the MAXNUMMP parameter. If the resourceutilization option
value exceeds the value of the MAXNUMMP on the
server for a node, the backup can fail with an Unknown System Error message.
- You can get a multi-session restore from your single restore command,
and from a single volume on the server, if that volume is device class
FILE.
For example, if the data you want to restore is on 5 different
tape volumes, the maximum number of mount points is 5 for your node,
and resourceutilization is set to 3, then 3 sessions
are used for the restore. If you increase the resourceutilization setting
to 5, then 5 sessions are used for the restore. There is a 1 to 1
relationship between the number of restore sessions that are allowed
and the resourceutilization setting. Multiple
restore sessions are only allowed for no-query restore operations.