Re: Replication or copy

From: Kevin Grant <K.Grant_at_nowhere.com.au>
Date: 28 May 2001 23:49:09 GMT
Message-ID: <Xns90B06389196C8KGRANTBNEQLDAU@132.234.250.31>

"Sybrand Bakker" <postbus_at_sybrandb.demon.nl> wrote in news:th3sev1joqb815_at_beta-news.demon.nl:

>
> "Johan Lorier" <johan.lorier_at_nl.abb.com> wrote in message
> news:c4ce07bf.0105272159.4b65633a_at_posting.google.com...

>> Hi all,
>>
>> i need a copy of an OLTP database, that will be used as a DSS. I think
>> I have 2 options: 
>>
>> 1 - Every night make a copy of the db-files to the DSS server
>> 2- use replication
>>
>> Can anyone point me to (dis-)advantages of these options, especially
>> about performance issues? 
>>
>> Thxs a lot.

>
> Option 1 will simply not work at all, or the OLTP database needs to be
> down during the event. This is necessary because otherwise you will be
> getting inconsistent copies. If the database is down during copy you
> will also need to recreate the controlfile.
> So, just forget about this scenario: it is not going to work

Option 1 does work. Every night we make a clone copy of our production database (without bringing it down) by copying the datafiles.

There are a couple of pre-requisites however:

• The production database must be in archive log mode.
• Each tablespace must be in backup mode when copying its datafiles.

The whole process goes something like this:

For each tablespace do

        Start backup mode;
        Copy datafiles to remote clone location;
        End backup mode;

done;
Copy applicable archive log files to remote clone location; Create control file for clone;
Recover clone;
Startup clone resetlogs;

Overall it's a complicated process but, as with anything, with practice it becomes a whole lot easier.

We've written a script which does all the hard work for us. Now we just schedule the job in cron and when we arrive in the morning we have a brand spanking new clone database ;)

Kev. Received on Mon May 28 2001 - 18:49:09 CDT