Re: Database Mirroring

In article <3ri3co$s09_at_linus.mitre.org>, mah_at_reaper.mitre.org says...
>
>Oracle supports the Parallel Server option. This incorporated with
>some Clustering software should allow you to have an Oracle instance
>on two seperate machines sharing a common set of data files via a
>shared SCSI bus. The Cluster Softwares locking mechanism must conform
>to a set of Oracle standards though.
>
>William Lee (william.lee_at_cwolhk.com) wrote:
>: Hi,
 

>: >From: Donita Hilfinger <hilfinge_at_rose.rsoc.rockwell.com>
>: >Does anybody know if there is a way to mirror an Oracle database? We
>: >are required to be able to switch over to a secondary system if the
>: >primary fails within minimal time?
>: >Does Oracle support fault tolerance through the software similar to
>: >what DEC SAFE Server does through hardware?
 

>: If your O/S support disk mirroring, try using it.
>
>
>: William.
>: william.lee_at_cwolhk.com
>: ___
>: * UniQWK #5138*
Should concern the short period of data inconsistency among multi-instances in parallel servers. There is a parameter PROPAGATION_DELAY which is undocumented in Oracle manual to control this inconsistency period in millisecond. Too short of this value will serialize all transactions among servers. Must be very carefull in tuning this parameter. All those parallel servers, disk mirroring or RAID 0 only protect failure on instances and physical disk failure. But the most critical and common failure which is file failure still relies on the ARCHIVED logs. To protect this failure with instantaneous recovery or what we called NON-STOPPED system, you need to to consider an automatically diseater recovery system which is not available as package on macket. We have such system design on hand which involves a lot of resources in term of hardware and development resources.

In fact, the idea is so simple. Oracle snapshot is adapted to propagate data to the secondary server. Oracle Signal is adapted to monitor the status of both systems. But the most difficult is to determine the actual point of failure among all possibility.

Good luck, Fault-Tolerance is most interesting stuff in database design.

Steve. Received on Mon Jun 12 1995 - 00:00:00 CEST