Re: Transparent Application Failover Clarification

"Prem K Mehrotra" <premmehrotra_at_hotmail.com> wrote in message news:43441e77.0406171912.29af73bd_at_posting.google.com...
> I have read that TAF can be used for standby database, data guard,
> RAC, shutdown/restart of a database instance, etc. TAF seems like an
> interesting feature for resume of select statements. My question is,
> where does Oracle store information
> about select statements, state of database etc when TAF is used to
> switch to
> fail over database.

The database is not what is being failed over. It's a user's session that is being re-connected. So guess where the information about where a select statement is up to gets stored? Correct: on the client. Which is why the SELECT TAF configuration is not the default, and isn't a free gift. A user's session is burdened with processing the "you are at row 356", "you are at row 357" information for every select statement issued, even when no failover actually takes place.

> Information is obviously not in the database
> instance. Is it
> on client, if yes where.

"Memory". You can't look at it, so the question is a bit moot. You answer your own question lower down anyway: 'in memory of client process'. About as accurate as it needs to get.

> I know only those applications which use OCI
> underneath directly or indirectly can make use of TAF. So, is
> information
> about select statements stored in memory of client process (i.e. in
> client process which has linked with OCI libraries)? What is the
> overhead of TAF since
> it has to maintain information about the select statements

Considerable. Not unbearable, but considerable.

Regards
HJR Received on Thu Jun 17 2004 - 22:29:28 CDT