Re: Platform + version migration, no downtime?

Sybrand Bakker <gooiditweg_at_sybrandb.demon.nl> wrote:

>day. I would have probably cloned the original 8.1.7 database to a new
>database, and migrated the new 8.1.7 database to 9ir2 using the
>migration assistant, and this procedure would have been -as the
>database format doesn't change- a piece of cake.

Yes, a piece of cake. But I preferred to go the exp/imp way since it was affordable (in the small db case) while keeping control of things. I am an ambitious DB admin :-)

>>I am wondering if it is possible to do the transition in parts, one
>>schema at a time, without disturbing normal work. But setting up a DB
>>link for moved schemas does not seem to be a solution because too many
>>scripts would have to be changed and tested; something would break. I
>>am not aware of any other "trick" to implement a distributed DB.
>
>Synonyms exist. Synonyms can point to an object in a remote db. I
>don't consider this to be a trick, and I don't see which scripts would
>need to be tested.

You strike me, really. If you begin replacing things with synonyms pointing to a db link, what is going to be your expectation concerning performance? The DB could become fully unusuable, because too slow. You would have to TEST FIRST.

>> In a second step,
>>a replication between the two platforms (Sun and Linux) would be setup
>>and let run smoothly until replication is complete, while work keeps
>>going in the source DB; finally, only switching to the new platform by
>>a simple tnsname change would be necessary.
>>
>>Doing migration in place is a little bit risky, so I think that I
>>would need a cold backup first, adding 10 hours to the procedure.
>>
>
>Migration in place would only change the datadictionary. The datafile
>format doesn't change.

I have read other opinions stating that the procedure is not safe.

>>But the crucial question here is if it is possible to do an online
>>replication of databases of the same Oracle version but on different
>>platforms... Is there something like a logical replication?
>
>(Advanced) replication by means of snapshot is by design logical. It
>is not going to work however, because replication only tracks changes,
>and the replicated database consists of snapshots, not of tables. You
>would still need to 'convert' your snapshots to tables.

Not if doing it right: Multimaster Replication.

Regards
Rick Denoire Received on Mon Jan 12 2004 - 18:12:26 CST