Recovery

Recovery is the key motivation for using several disk devices. You can ensure full recovery by storing a database’s log on a separate physical device. You can also mirror database devices to achieve nonstop recovery.

Storing logs on a separate device – unless a database device is mirrored, full recovery requires that a database’s transaction log be stored on a different device from the actual data (including indexes) of a database.
In the event of a hard disk failure, you can create an up-to-date database by loading a dump of the database and then applying the log records that were safely stored on another device. See System Administration Guide: Volume 2 > Creating and Managing User Databases for information about the log on clause of create database.
Disk mirroring – Nonstop recovery in the event of a hard disk failure is guaranteed by mirroring all SAP ASE devices to a separate physical disk. See System Administration Guide: Volume 2 > Mirroring Database Devices.