Re: Combining Data Guard with clustered redo logs for high performance standby

From: Mark Bole <makbo_at_pacbell.net>
Date: Tue, 16 Aug 2005 21:19:06 GMT
Message-ID: <eLsMe.1990$r54.227@newssvr19.news.prodigy.com>

Dennis G Allard wrote:

[...]

>>
>> If you trust your external storage array, why not put your whole 
>> database on the external array, since you are already putting the 
>> control files, online, and archived redo logs there?  Do you know that 

>
>
> As a matter of fact, I have decided to do just that! Because then I
> could use the active/passive failover technique by simply installing
> Oracle on a backup server but keep it turned off. Fail over would
> cause the backup server to mount the external disks and bring Oracle
> up (and, for that matter, take over the IP of the failed primary
> server).
>

This is exactly what products like HP/UX Service Guard and Veritas VCS have provided for many years.

>> having a physical standby requires another full Oracle license (false 
>> claims to the contrary not withstanding)?  Do you know that Oracle 

>
>
> I just attended Linux Expo in San Francisco last week. Oracle reps
> stated that they have a 'ten day rule' -- as long as you don't use
> the standby server database more than ten days in the year, there is
> no license fee.

Read the following document, the section on "Backup/Failover/Standby".

http://www.oracle.com/corporate/pricing/sig.pdf

The confusion arises because of sloppy use of the words "standby" vs. "failover".

To summarize: if you are applying redo to a separate copy of the database (meaning you have to mount the database), it is a standby and requires a license for the server that runs it. If you are simply moving the primary database from one node to another via mounting and unmounting shared storage, it is a "failover" and the ten day rule applies.

[...]
>
> My only issue with Data Guard is the potential performance hit. It seems
> you agree that using LogXptMode = SYNC is expensive but ASYNC or ARCH
> modes are tolerable. Is that correct?
>

No, because I have never used Data Guard "maximum protection" mode, but if I did, I would measure the performance "hit" first to see how bad it was before concerning myself with steps to address it.

-Mark Bole Received on Tue Aug 16 2005 - 16:19:06 CDT