RE: Some Dataguard is good, lots more must be better? (specifically, when do most actual failovers really occur?)

Well, here come a few things:

• separate: use DG for database and OS snapshots for OS stuff.
• keep it clean: eliminate all kind of scripts from db server machine except of tightly controlled.

I find it quite logical. High Availability must take the whole system into account not only database alone.
What if application server goes down, etc? However DG is quite good in keeping the most complicated part - database - protected. The other parts must be protected somehow as well.

Now regarding DG with time lag. Well, it is not a good option for maximum data protection(as Oracle defines it.) At least I do not know how to protect redo logs in this mode. Which means that for maximum data protection you have to have a standby database which is in complete sync, i.e. running in maximum protection mode(at least most of the time.) BUT I am not sure if file system snapshot technique can achieve this either.

Which means that you need yet another database with time lag. This configuration can protect from accidental table truncates (drops can be undone in 10g with recycle bin - provided it is not too buggy.) 10g has a flashback option. I've never tested but it may be that you can flashback a pshysical standby which means that same standby can serve both purposes(again - most of the time but not 100% of time). However for that I believe you need a flashback area with flashback logs - the question is how much space they take per 1h for example?

If you go into
http://www.scaleabilities.co.uk/book/ScalingOracle8i-CreativeCommons.htm then you can find a nice example of HA design at the end of the book (in case study chapter) It has 4(!) databases if my memory serves me right.

-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Kevin Closson Sent: 20. september 2006 16:33
To: oracle-l_at_freelists.org
Subject: RE: Some Dataguard is good, lots more must be better? (specifically, when do most actual failovers really occur?)

 >>>The OS mirror issue means that system admin must 

>>>for example, for me as DBA it was no issue to keep in synch and
>>>activate all scripts, jobs, etc at the standby machine.
>>>

herein lies the main concern I have. DG is great for keeping a database replicated, yes, but upon switchover there needs to be the total environment there...all the stuff the site has **outside** the database for the workflow.
Such things as UTL_FILE stuff, external tables, scripts, etc... seems storage level would be the only way to have the operations environment replicated.

--
http://www.freelists.org/webpage/oracle-l


Fyrirvari/Disclaimer
http://www.landsbanki.is/disclaimer
--
http://www.freelists.org/webpage/oracle-l