Re: 9i DataGuard, RAC primary - secondary offline for networkmaintenance

On 12/6/06, Ric Van Dyke <ric.van.dyke_at_hotsos.com> wrote:
>
> Carel-Jan,
>
>
>
> You are very correct that as stated in the documentation the version of
> Oracle are supposed to be the same (as in identical) on the primary and the
> standby. However I worked with the folks who developed the standby database
> code and this is more of a CYA requirement then a real one. There was some
> long discussions about this requirement and I believe that "paranoia" won
> out, the idea being it's better to be over restrictive then not. The issue
> is more about the format of the redo log stream then anything else. It's
> very likely that this setup will work just fine. And given that Tony
> (apparently) has been running with this setup for some period of time, it's
> again likely that this will continue to work just fine.
>

My take on this is that this is merely the technical issue as to whether the standby database will physically work. I don't see it as the important issue here at all. I think there are at least 2 likely more important issues.

First is the support issue, it may not be a likely scenario, but people invest in DG precisely because they value extremely highly the availability and supportability of the platform that their data is on. Otherwise the logical thing to do is no standby or a cheaper solution for HA. It doesn't make any sense to me to spend those dollars and man-hours getting the thing setup and then make it unsupported.

Second is the fact that generally it isn't the data that people want to make available, but the data and the applications that access that data. Here we are specifically told that the application mandates a lower patchset than the standby is at. In otherwords in the event of a switchover or failover the application is at a non-mandated patchset level.

Now for sure this all may well work perfectly practicably, but it does rather raise the General's question about a nuclear deterrent "What the **** is the thing for?" It's back, for me, to a common fault of DBAs (myself most definitely included this isn't aimed at the OP) that we consider carefully technical issues and forget the business issues that are at the root of the technical course of action in the first place.

-- 
Niall Litchfield
Oracle DBA
http://www.orawin.info

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