Re: Multimaster replication as alternative backup

VirVit,

You haven't specified Oracle version and your tolerance for data loss. If you can afford to lose the data in the most current redo log file, then I would suggest 9i Data Guard in maximum performance mode (or Standby in 8i) solution over the MM replication. The DG solution does not affect the primary database performance. You can backup the standby database and use it for recovery of the primary, too.

If you can't afford to lose any data, then you can still use the DG Maximum Protection (in 9i) mode, but it will affect the performance to some extent. However, in this case (no data loss) you have to enable MM Synchronous Replication as opposed to the default Asynchronous mode. In the Synch mode, the performance is worse compared to the Max Protection DG solution.

Here is a summary of the options:

Oracle 8i
|
+-> Last redo data loss ok => Standby Database ~~ Performance=BEST +-> LAst redo data los NOT ok => MM Synchronous Replication ~~ Performance=VERY BAD

Oracle 9i
|
+-> Last redo data loss ok => Data Guard Max Performance Mode ~~ Performance=BEST
+-> LAst redo data los NOT ok =>

     |
    +-> Option 1: MM Synchronous Replication ~~ Performance=VERY BAD     +-> Option 2: Data Guard Max Protection Mode ~~ Performance=BAD

Therefore, you are better off using DG (or standby in 8i).

Pros:
(1) You can use standby datafiles to recover primary database (2) You can take RMAN backups from the standby, reducing the CPU cycle requirements in primary

Cons:
(1) In Max Protection Mode, the primary also halts if the standby has a problem; not truly a HA solution. Ideally you need three or more servers - one primary and two standbys to work perfectly => high cost

Summary: If your management can live with the loss of the last redo, your best option is DG Max Performance (or Standby, in 8i), IMHO.

HTH. Arup Nanda
www.proligence.com

• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Tuesday, November 18, 2003 11:54 PM

> Hello!
>
> What do you think of additional backup method as multimaster replication?
> Isn't it a way to continue working normal, if main database crash and I
move
> all connections to another master site?
>
> --
> Oracle 9i DBA beginner
>
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: VirVit
> INET: virvit_at_prodtorg.udm.net
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-- 
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-- 
Author: Arup Nanda
  INET: orarup_at_hotmail.com

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