Re: Ambiguities regarding Oracle High Availability features

On 2004-12-31, Sybrand Bakker <sybrandb_at_hccnet.nl> wrote:
> 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 OPS = Oracle Parallel Server, available from 6.0 Has been replaced by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.

        They can be. You have to specifically set it up that way. You may not want it set up that way and there are other more asynchronous options available. You can even replicate transactions by whole archive log (which is the "classic" 8i version of the feature).

>
>
> 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.

        This feature can't handle LONG data types in 9i. If you have some shoddy 3rd party apps, then this feature becomes unusable.

[deletia]

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