Restoring from Multiple Devices (RESTORESET)

Sequential Devices

You can use sequential device configuration when you have a large set of files to RESTORE from a number of tapes and you want to speed up the process. The sequential device configuration is described under "Using Tape Devices Sequentially," in Chapter 3, "Preparing Storage Devices."

To RESTORE files from sequential devices:

For example, to RESTORE files from three sequential devices, use the following set of commands:

   :FILE SEQ1;DEV=7

   :FILE SEQ2;DEV=8

   :FILE SEQ3;DEV=9

   :RESTORE ;@.@.@;RESTORESET=(*SEQ1,*SEQ2,*SEQ3)

	NOTE: Do not back reference the filename of a tape device immediately before the name(s) of the file(s) you are restoring when using the RESTORESET parameter. Instead use a placeholder for the missing parameter normally supplied when using a single tape device. The placeholder is provided by the use of the first semicolon (;) in the RESTORE command.

The above RESTORE command restores all system and user files from three sequential devices. The parentheses surrounding back-referenced filenames group the devices into a device pool.

When RESTORE has transferred all the files from the first tape on the first tape device, it immediately begins restoring files from the second tape on the second tape device. While RESTORE continues, you can unload the first tape and mount a new tape on the drive. When RESTORE finishes restoring the files on the last device, it reverts to restoring files from the first device. The process continues to cycle through the devices in the device pool until it has restored all the files you specified.

If you gave the tape devices a single filename such as:

   :FILE T;DEV=TAPE

Enter the following RESTORE command to RESTORE files from a set of three sequential tape devices:

   :RESTORE ;@.@.@;RESTORESET=(*T,*T,*T)

You can RESTORE files that were created using parallel devices or parallel device pools in a sequential configuration. For example, to RESTORE a set of reels that have been created using parallel device pools, you must use the following logical order to mount the reels on sequential devices: A1, A2....B1, B2 and so on. (The first alphabetic character, in capital letters, indicates an original, unique parallel set; the second numeric character indicates an original sequential reel within the set.) That is, mount A1 first, followed by A2. The reel that you mount prior to B1 should be the last "A" reel.

	NOTE: Sequential RESTORE is not available for labeled tapes.

Parallel Devices

A parallel device or parallel device pool configuration can be used for restoring files. Therefore, you can use the same designations with the RESTORESET parameter that you can use with the STORESET parameter. Refer to Chapter 3, "Preparing Storage Devices," for information on storing to multiple devices.

If you gave the tape devices a single filename such as:

   :FILE T;DEV=TAPE

Enter the following RESTORE command to copy files from a set of two parallel tape devices:

   :RESTORE;@.@.@;RESTORESET=(*T),(*T)

Describe parallel devices in the RESTORESET parameter by enclosing each back-referenced device filename within parentheses. Use commas to separate devices.

To RESTORE files from parallel device pools, use parentheses to group the devices into pools. Separate the devices in the pool from one another with commas. Commas also separate each device pool.

For example, the following commands copy files from two parallel device pools. Each device pool contains two sequential devices. In the following example, RESTORE uses a total of four devices divided into two device pools.

   :FILE PPA1;DEV=7

   :FILE PPA2;DEV=8

   :FILE PPB1;DEV=9

   :FILE PPB2;DEV=11

   :RESTORE ;@.OPERATOR.SYS;RESTORESET=(*PPA1,*PPA2),(*PPB1,*PPB2)

If you gave the tape devices a single filename such as:

   :FILE T;DEV=TAPE

Enter the following RESTORE command to copy files from a set of parallel device pools:

   :RESTORE ;@.@.@;RESTORESET=(*T,*T),(*T,*T)

	NOTE: Parallel RESTOREs can be performed only with tape sets that were created with a parallel STORE parameter. A sequential RESTORE can be used with any tape set. Parallel RESTORE allocates every subset of the tape set (for example, STORESET=(*T1),(*T2) creates two subsets) to distinct parallel devices or device pools, and expects a volume belonging to the subset to be mounted on its allocated device or device pool only.