Mirroring with DRV

DRV (Dual Recording by Volume) is a method of recording in which the BS2000 input/output system maintains its data on two disks. The DRV procedure is also referred to as dual mode.

The interfaces for DRV are provided by the software product DRV zur Verfügung. For further details, please refer to the “DRV” manual [3].

On the other hand, with the SRV procedure (Single Recording by Volume) input and output of data can only be carried out on a single disk. As a result, the SRV procedure is also referred to as mono mode.

FDDRL always occupies disks using SPECIAL occupancy. As a result, disks are not saved and restored as DRV disk pairs, but rather always in the form of single disks. The DRV parameters as set in the Standard Volume Label are also saved and restored.

DRV disks can be saved using the following methods:

1. Saving without DRV operation

   DRV disks are usually saved in the same way as SRV:

   >	Export pubsets. Take private disks out of operation using /SET-DISK-PARAMETER ASSIGN- TIME=*USER.
   >	Then only save one disk of each disk pair.
   >	After the save has been completed, return DRV disks to live operation, dual mode is then possible again.

2. Saving consistent disk statuses with a short period of interrupted operation

   The applications of a DRV disk are only interrupted for a short period of time. One of the disks continues to run in mono mode, while the other disk of the pair is saved.

   >	Take the DRV disk pair out of operation.
   >	Deactivate dual mode (/STOP-DRV-DUAL-MODE).
   >	Put the disk or pubset into mono mode operation.
   >	Save the split disks; You can rename pubsets beforehand using PVSREN.
   >	After the save is completed, reactivate dual mode again (/START-DRV-DUAL-MODE).  This automatically starts a DRV restoration.

3. Splitting and saving disks during live operation

   It is possible to split disks during live operation. However, when you do this, a crash-consistent data status is only created for private disks and single disk pubsets. For pubsets with more than one disk it is not sensible to split disks during live operation, since the inconsistency of the F5 labels that may result from saving the disk may require the entire disk to be saved, including the areas that have not been allocated.

   >	After saving, use /START-DRV-DUAL-MODE to start dual mode again. A DRV restoration of the disk will be necessary as a result.