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Tivoli Storage Manager for Windows Backup-Archive Clients Installation and User's Guide

Restoring Large Amounts of Data

With Windows NT, if you need to restore a large number of files, you will get faster performance using the command line interface rather than the GUI interface. In addition, you will improve performance if you enter multiple restore commands at one time. For example, to restore all the files in your c: file space, enter:

   dsmc restore c:\* -subdir=yes -replace=all -tapeprompt=no

However, if you enter multiple commands for the root directories in your c: file space, you can restore the files faster. For example, enter these commands:

   dsmc restore c:\users\ -subdir=yes -replace=all -tapeprompt=no
   dsmc restore c:\data1\ -subdir=yes -replace=all -tapeprompt=no
   dsmc restore c:\data2\ -subdir=yes -replace=all -tapeprompt=no

Or, if you need to restore files for multiple drives, enter these commands:

   dsmc restore c:\* -subdir=yes -replace=all -tapeprompt=no
   dsmc restore d:\* -subdir=yes -replace=all -tapeprompt=no
   dsmc restore e:\* -subdir=yes -replace=all -tapeprompt=no

You can also use the quiet option with the restore command to save processing time. However, you will not receive informational messages for individual files.

Note:
If you already have the appropriate values set for the subdir, replace, tapeprompt, and quiet options in your client options file, it is not necessary to include these options in the commands.

When you enter multiple commands to restore your files, you must specify a unique part of the file space in each restore command. 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:

   dsmc query backup -dirsonly -subdir=no c:\

As a general rule, you can enter 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 network utilization and how much memory you have. For example, if \users and \data1 are on the same tape, the restore for \data1 must wait until the restore for \users is complete. However, if \data2 is on a different tape, and there are at least two tape drives available, the restore for \data2 can begin at the same time as the restore for \users.

The speed at which you can restore the files also depends upon how many tape drives are available and whether your administrator is using collocation to keep file spaces assigned to as few volumes as possible. If your administrator is using collocation, the number of sequential access media mounts required for restore operations is also reduced.

No Query Restore

When you enter an unrestricted wildcard source file specification on the restore command and do not specify any of the options: inactive, latest, pick, fromdate, or todate, the client uses a different method for retrieving files and directories from the server. This method is called no query restore because instead of querying the server for each object to be restored, a single restore request is sent to the server. This request results in files and directories being returned directly from the server without further action by the client. The client merely accepts the data coming from the server and restores it to the destination named on the restore command.

An example of an unrestricted wildcard command would be:

c:\mydocs\1999\*
 

An example of a restricted wildcard command would be:

c:\mydocs\1999\sales.*

When the client uses this method, the restore session is treated differently. If the restore process is interrupted for any reason, such as a power outage or network failure, the server records the point at which the restore was interrupted. This record is known to the client as a restartable restore. It is possible to create more than one restartable restore session. Use the query restore command to find out if your client has any restartable restore sessions in the server database.

The existence of a restartable restore inhibits further backups of that file system until the restartable restore is completed. If you attempt to repeat the restore that was interrupted or try to back up the destination file space, the attempt will fail because the original restore was not completed. You can restart the restore at the point of interruption by entering the restart restore command, or you can delete the restartable restore using the cancel restore command. If you restart the interrupted restore, it will restart with the first transaction, which may consist of one or more files, not completely restored when the interruption occurred. Because of this, you may receive some replace prompts for files from the interrupted transaction which were already restored.

The differences between the standard restore process and the no query restore process are outlined below.

Standard Restore Process
  1. The client queries the server for a list of files backed up for the client file space being restored.
  2. The server sends a list of backed up files that match the restore criteria. If both active and inactive files are to be restored, information about all backed up files is sent to the client.
  3. The list of files returned from the server is sorted in client memory to determine the file restore order and to minimize tape mounts required to perform the restore.
  4. The client tells the server to restore file data and directory objects.
  5. The directories and files to be restored are sent from the server to the client.

No Query Restore Process
  1. The client tells the server that a no query restore is going to be performed and provides the server with details about file spaces, directories, and files.
  2. The server sorts the data using an internal sort table which minimizes tape mounts.
  3. The data to be restored is sent to the client. File and directory objects stored on disk are sent immediately since sorting for such data is not required before restoring it.

For more information on using the command line to begin restartable restores, see Restore. For help with performing restartable restores using a GUI, follow these steps:

  1. Click Help from the Restore window.
  2. Click Restoring Backup Versions
  3. Click Work with restartable restore sessions.


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