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If you need to restore a large number of files, you can improve performance by issuing multiple restore commands at one time.
You can use multiple restore sessions to improve performance. In this case, you can start several restore sessions simultaneously. See Resourceutilization for more information.
For example, to restore all the files in your sys:user file space, you could enter:
load dsmc restore sys:user/ -subdir=yes -replace=all -tapeprompt=no
However, if you issue multiple commands for directories in your sys:user file space, Tivoli Storage Manager can restore the files faster.
For example, you could issue these commands:
load dsmc res sys:user/jones/ -subdir=yes -rep=all -tapep=no load dsmc res sys:user/smith/ -subdir=yes -rep=all -tapep=no load dsmc res sys:user/brown/ -subdir=yes -rep=all -tapep=no
Or, if you need to restore multiple volumes, you could issue a restore command for each volume. For example:
load dsmc restore sys:* -subdir=yes -replace=all -tapeprompt=no load dsmc restore app:* -subdir=yes -replace=all -tapeprompt=no load dsmc restore data:* -subdir=yes -replace=all -tapeprompt=no
When you issue multiple commands to restore your files, you must specify a unique part of the file space in each restore command. Be sure that you do not use any overlapping file specifications in the commands.
To display a list of the root directories in a file space, use the query backup command. For example:
load dsmc query backup <filespace> -dirsonly -subdir=no
As a general rule, you can issue from two to four restore commands at one time. The maximum number you can run at one time without degrading performance depends on factors such as how much memory you have and network utilization.
The speed at which Tivoli Storage Manager can restore the files also depends on how many tape drives are available, and whether your administrator is using collocation to keep file spaces assigned to as few volumes as possible.
For example, if sys:user/jones and sys:user/smith are on the same tape, the restore for sys:user/smith must wait until the restore for sys:user/jones is complete. However, if sys:user/brown is on a different tape, and there are at least two tape drives available, the restore for sys:user/brown can begin at the same time as the restore for sys:user/jones.
If your administrator is using collocation, the number of sequential access media mounts required for restore operations is also reduced.
Other options you can choose to use in multiple restore commands are: