Re: Ambiguities regarding Oracle High Availability features

On 31 Dec 2004 04:36:10 -0800, qazmlp1209_at_rediffmail.com (qazmlp) wrote:

>I keep hearing about the following Oracle features w.r.t High
>Availability.
> - Data guard
> - Data Replication
> - TAF
> - OPS
> - RAC
> - Oracle stream
>
>I am bit confused about what features are available with Oracle
>versions 9i & 10g.
>
>Also, about
> - interworking/relation between these features For e.g. whether Data
>Replication is used by Data guard
> - whether 1 feature is a replacement for an another Oracle feature
> - what features are availabile only for Cluster environment
> - what features can be used for multiple clusters that are located
>many kms apart etc.
>
>Could anybody give consolidated information on all these?
>
>Thanks!

OPS = Oracle Parallel Server, available from 6.0 Has been replaced by RAC in 9i and higher.
Basic idea: two or more servers operate on one shared set of disks. If one server breaks down the other server takes over. TAF: Transparent Application Failover. This is a sqlnet feature. The client switches automagically to the other server, when one server breaks down. Can be used in conjunction with OPS/RAC.

Data guard: 9i marketing term for standby database. The standby database is on a physically fully separated system. *Transactions* are replicated, so the standby database is always up-to-date.

Data replication: available from Oracle 7 onwards. Has been replaced by Oracle Streams.
The basic idea you replicate objects every hour, every 10 minutes or whatever, to a different database anywhere.

Dataguard <> RAC <> Streams

The best consolidated information of course is to be found on http://otn.oracle.com

--
Sybrand Bakker, Senior Oracle DBA