ADSM-L

Re: [ADSM-L] Nervous Nellies and TDPO -- feasible?

2007-11-21 10:56:08
Subject: Re: [ADSM-L] Nervous Nellies and TDPO -- feasible?
From: CAYE PIERRE <Pierre.Caye AT ALCATEL-LUCENT DOT FR>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Wed, 21 Nov 2007 16:55:35 +0100
>       1) RMAN doesn't deal with non-transactional DB data loads well.
>          (i.e. data loaded not through the usual INSERT/UPDATE
>          methods, but done via sqlldr. This doesn't generate 
> redo logs.)
> 
>          True or false?

RMAN back-up data's which are in all tables, whatever they had been
loaded or inserted.

>       2) RMAN requires a recovery database be created to do 
> recoveries to
>          (instead of recovering to original 
> database/tablespaces in-place).
> 
>          True or false? I thought RMAN didn't need an 
> intermediate temp
>          database and could restore directly 'in-place'.

False. Rman is able to restore databases on original place, or anywhere
you wish. It only requier a large enough database.

>       3) Will RMAN guarantee a good point-in-time view of DB data?

It depend of the regularity and disponibility of redo logs, which need
to backed-up too...

>       4) Same as #3 above, but what if the DB is currently processing
>          a large series of INSERTs or UPDATEs or sqlldr run, will RMAN
>          only send data that was present at the moment of 
> backup start?

Rman perform backup wwhich will be consistent; whatever happend on the
db as insert delete, update and so. RMAN is a part of oracle product,
not an external actor, and act at a logical level of data's. At the end
of the rman backup, data's are consistent and could be restored in a
consistent state.

>       5) Does RMAN/TDPO use scale to really large DB setups? Say, tens
>          or hundreds of terabytes? Or even sub-10 TB?
> 
>          Anybody using TDPO well with terabytes of Oracle data? (I
>          think they're hoping for assurances that it really does work
>          in the real world at that scale.)

I'd only experienced db of 2/3 Terabytes and it work fine, whithout any
particular configuration on Oracle side.
See Oracle guides for best practices concerning very large databases.

>       6) How does Oracle RMAN know what rows to send for an
>          incremental backup? Does Oracle maintain a bitmap of 
> some kind
>          or time-based logging of changed blocks or something? Any
>          pointers to whitepapers or information on how it works behind
>          the scenes?

On Oracle 10g, Oracle maintain a bitmap of changed block.
So incremental backup are faster than full backup on 10g. 
On Oracle 9i, Oracle scan all filespaces for changed block.
So incremental backups can be slower that full but, from my experience,
it is almost the same.

>       They would prefer to utilize Veritas DB Edition (DBED) 
> checkpoint feature which is where a script runs to put all 
> tablespaces in backup mode, brings DB-based filesystems to a 
> consistent state, generate a checkpoint (snapshot-like) of 
> the filesystem, then brings all tablespaces back to online 
> mode. The TSM BA client then mounts the most recent 
> checkpoint R/O then backs it up at the file level.
> 
>       The problem with the above approach is this essentially 
> results in what amounts to a full backup every single time it 
> kicks off. That's just not practical in terms of tape cost as 
> well as the length of backups.
> 
>       I see TDPO as the only practical choice for much faster 
> and more frequent backups (and restores) and is guaranteed 
> for consistent point-in-time views of DB data. The BA client 
> was also not meant to back up databases (though it *could* do 
> so if properly quiescied).

Nothing more to said. You're right. TDPO act only as a library manager
for RMAN. It is RMAN which is the principal actor on back-up.
RMAN is an integrated Oracle solution to backup Oracle databases.
Integrated mean that it work fine at logical level of the data's. The
use of RMAN, for offline (full) or online (incremental) backup is a
guarantee for consistencies of backed-up data's. 
You work with Oracle 10g, so incremental back-up will be fast and you
will save storage and time.

>       My issue? I don't have enough meaty information yet to 
> put concerns to rest, and I'd really like to make use of TDPO 
> after paying out $16,000. Any info would be much welcome.

Search on IBM/redbooks. There are redbooks about RMAN and TDPO (sorry I
don't remind reference number...).

Pierre