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 Availability 

You can use the appropriate features of your hardware, operating system, or database to optimize the availability of a database instance. Note the following recommendations:

·        Locate every volume type on a different disk.

·        In a production system, the log area should always be mirrored with hardware-based tools. Use RAID 5 or RAID 1 systems. Make sure that your RAID controller delivers good write performance, and that a cache is backed up to the disk even in a power outage.

·        If you cannot use hardware-based mirroring, then you can set the log mode of the database instance so that it uses software-based mirroring.

·        Use normal log backups. Do not allow the log area to be overwritten.

To make sure there is always enough space to write the log entries, make regular log backups.

·        Always have redo log management activated.

·        If you want to ensure a high standard of availability, we recommend using RAID-5 or RAID-1 configurations for the data area. A disk crash and change will then not affect the operation of the database, if the RAID system is able to perform a corresponding recovery procedure.

·        In a production system on UNIX, data volumes and log volumes should be located on raw devices. Raw devices achieve better performance, and can be more securely controlled in the event of a system failure.

·        When using fault-tolerant hardware, it is best to only use the same type of hardware when you want to extend the capacity. For example, only extend RAID-5 systems with RAID-5 systems and mirror disks with mirror disks.

See also:

High Availability

 

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