Re: 9i RAC and LOG_ARCHIVE_DEST_n on OCFS

Howard J. Rogers wrote:

> Notice that the documentation says L_A_D_n is optional for being identical!
>
> I realise the documentation also says in the immediately preceding sentence
> 'parameters [which] must be identical on every instance'. How you can have
> an 'optional' 'must' is one of life's (and Oracle's documentation's) little
> mysteries.

Ok, let's go for 'optional was just a bad synonym for under some circumstances'.

> Now, Oracle itself publishes information about the NFS share technique...
> and it is another sign of temporary madness in their documentation
> department that they would do that AND simultaneously say the LADn "must"
> be the same on all instances... because the two are essentially mutually
> contradictory.
>
> So... ignore the stuff about the parameter needing to be identical. That's
> just tosh.

Exactly. This part was the other reason for my concerns, since it is such an obvious inconsistence in this part of documentation.

I still had that other bit in mind, on using ARCHIVE_LAG_TARGET:

"Caution:
The ARCHIVE_LAG_TARGET parameter must be set to the same value in all instances of an Oracle Real Application Clusters environment. Failing to do so results in unspecified behavior and is strongly discouraged."

It's just that I don't want the thing to behave nastily (maybe on recovery time) because I misread the documentation ...

> On the other hand, I'd also ignore the stuff about fragmenting the OCFS. As
> I understood that presentation you mentioned, he was saying to keep
> archives away from datafiles and that one of the weaknesses of OCFS was
> that there was no defragmentation toolset for it.
>
> Well, the first bit is obviously true. Archive writing is I/O intensive
> stuff, and you don't want that I/O anywhere near your data files. But the
> lack of defragmentation tools for OCFS doesn't (IMO) mean that OCFS will
> inevitably fragment just because all instances decide to write to the same
> archiving location.
>
> Unless you're getting obviously archiving-related waits, I'd suggest all
> archives *should* be written to one OCFS directory, actually (obviously
> there's an I/O conflict concern there, but that's what striping is for).
>
> But if you want to keep them separated... different LADn's are just fine.
>
> Regards
> HJR
>

Another reason for us to split directories is even more simple: We have to move archive log files to the backup location on another machine - listing (yes, with ls) them takes a significant amount of time already after some hours. Since this is one of the ocfs inherent drawbacks, I prefer the "one separate partition with one dir per thread" approach over having some houndred/thousand files all in one directory.

Thank You, Howard
Steffen

-- 
... Steffen Roegner, Oracle dba
-------------------------------
http://www.sroegner.de, http://www.gagabut.de