emc BCVs and oracle databases

[wyan lowe]

Hi,

This isn't exactly HPUX question, but kind of is, since people might be using EMC BCVs to do backups of oracle databases via scripts.

I just read on page 16 of an EMC whitepaper "Oracle7 and EMC TimeFinder: certified best practices" that "Control files and redo logs should not be paired or split".

Does anyone know what this means?
And why?

the whitepaper is at: www.emc.com/partnersalliances/einfostructure/developers/white_papers.jsp

or you can do a search for "whitepapers" and select the link that corresponds to above url

Thanks,

[John Palmer]

I presume that they are talking about a 'hot' backup without taking the database down.

If this is the case (I couldn't find the reference that you mentioned) then this is reasonable because you can't guarantee that the control files or redo logs are ever in a consistent state. The tablespace files are because you 'begin backup' on them and Oracle keeps them consistent.

In a cold backup with the database shutdown (just while you split off a copy), this is not a problem.

Hope this helps,
John

[wyan lowe]

Hi John,

Thanks for the info. yeah, I didn't put in there the preceeding line: ;)

"An expected common usage of BCV devices will be for backups of Oracle data files. In order for the backups to be supported, the split of BCV devices must occur after the corresponding Oracle tablespaces have been placed in hot backup mode. Control files and on-line redo logs should not be paired or split. The BCV devices can also be split when the database is successfully shutdown."

The URL seems to work, there's a link on that page entitled Oracle7 & EMC Timefinder, Certified Best Practices, but the doc is only 16 pages and is only sort of useful.

I mean the reason I'm hoping for further explanation is because it seems on other posts (deja.com) seems the common practice doesn't mention this seemingly very important step...Nobody seems to say - yeah, that won't work.

If you have your control files & online redo logs on Standard HyperVolumes that are paired with BCV volumes then undergo the "split", does that mean you have a problem/bad backup, even if in hotbackup mode?

[Stefan Farrelly]

I think theres 2 ways you can do it, 1. is to use EMC's EDM product;

"Oracle and EMC have worked together to put hooks (api calls) into Oracle 8 so that oracle can go into a read-only mode, oracle issues the commands to EMC to use
timefinder to mirror the data, and then go back into a full read-write mode updating any transactions from the log files while that 2 or 4 minutes went by... It is just amazing... With EMC's EDM product, he will backup your data from the DISK itself and never bother the server."

The second is to use Oracles EBU/RMAN to do a hotbackup, but im not sure if this creates a backup file elsewhere or simply freezes the redo logs so you can then backup online without having to shutdown Oracle (ie. use TimeFinder). Were implementing ours now, wont know for another week.