The availability of a serverdb can be increased by using the corresponding hardware, operating system, or database features.
For mission-critical applications, we recommend RAID-5 configurations as disk peripherals for data devspaces. Then a failure and the exchange of a disk does not impair database operation. For performance reasons, the log devspaces must not be created on RAID-5 systems but on special disks.
The same applies to operating system mirror disks. These, however, require double disk capacity.
Regardless of the hardware and operating system properties, ADABAS provides a mirroring of the system devspace and all data devspaces. (Independent of these mirrored devspaces, log mode DUAL can be used to define mirrored archive log devspaces.) Mirroring the system devspace and the data devspaces is controlled by the configuration parameter MIRRORED and requires the definition of a corresponding number of mirrored devspaces. In a mirrored configuration, read operations alternate between the original and the mirrored devspace; write operations concern both devspaces.