Re: Oracle 10g on AIX 5.2 - i/o configuration

DA Morgan wrote:
> Be sure you give a lot of thought to Flashback area too.

hrmmmm.... hey that brings up an interesting question... just curious, but what are your general impressions of flashback area?

i tried it out and decided *not* to use it on our production 10g DB.

1. it doesn't really give you any *new* functionality... well, i mean all it enables is "FLASHBACK DATABASE" which is just a faster easier way to do PITR. but you can still just restore, recover, roll forward to that same PIT the way you've always done it. admittedly, flashback database is a *LOT* easier but i can't imagine wanting to flashback the ENTIRE database unless it was a rather catastrophic problem... especially considering that i have multiple applications each in their own schema on that DB and flashing the whole thing back would roll back changes in all the apps. anyway... i can still see where it would be nice BUT:
2. it seemed to be generating a fairly decent amount of IO. seems like it was generating about as many flashback logs as there were archive logs.

and my main reason...

3. i'm using OCFS (v1) on linux... OCFSv1 isn't the most robust implementation for handling filesystem metadata. (v2 will supposedly be much better but i haven't had a chance to play with it yet.) in fact seems like i remember the guys on the OCFS mailing list recommending having archive log destinations on different volumes for each node to reduce contention for DIRNODES - where the metadata is stored for OCFS files. we do this at our site on our production 9i and 10g RAC db's.

to enable flashback you have to use OMF which means that all the flashback logs have to go in the same location (for both nodes). if there is heavy activity then there would be a lot of flashback log generation and deletion by both instances in the same OCFS directory. odds are it would work fine but i'm not very comfortable with it.

SO... my conclusion was that if i could use ASM them i'd put the database in flashback mode. but with OCFS v1 i wasn't comfortable going there yet. And of course even without the DB in flashback mode you can still do flashback query, flashback table, flashback drop... you just can't flashback the whole DB. (But you can still do old fashioned PITR - and it's simple with RMAN.)

so i'm curious, has anyone else had any real experience or done any heavy testing with the database in flashback mode? do my observations seem in line? any other thoughts?

jeremy Received on Tue Jun 14 2005 - 10:36:36 CDT