In BS2000, it is possible to use a variety of methods for transparent data mirroring, e.g. DRV (Dual Recording by Volume), SRDF (Symmetrix Remote Data Facility) or TimeFinder.
UDS/SQL can use this transparent mirror data. This greatly increases the error-tolerance of the corresponding files since they are present in duplicate. If one unit fails, operation can be continued from the mirror disk without interruption
However, following a system crash it is possible that the two units will have different states which must first be aligned.
If DRV is used then, for example, BS2000 supports the automatic alignment of the DRV disks following a crash. However, this process can result in very long reconstruction times since the operating system has to read and write the entire disk. The DBH and the utility programs therefore perform a suitable alignment of those database areas that have differing states. This makes a potentially more time-consuming alignment operation by the operating system unnecessary.