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Re: Logical StandBy question

From: Stephane Faroult <>
Date: Wed, 12 Nov 2003 11:14:26 -0800
Message-ID: <>

Walt Weaver wrote:
> Stephane,
> What sort of problems can one expect from logical standby?
> I'm toying with the idea of using it as a replication database -- no
> additional schema objects will be created, but users will have read-only
> access to it. It's one of the options I'm looking at.
> Seems to me like there was a thread on this a few months ago, but I'm
> not sure...
> --Walt


This is basically my feelings after the tests :   o Properly monitoring is rather difficult. You must check at both ends to have more than a vague feeling that things could have gone awry. This is just one aspect of a general user-friendliness which first shows up in a 26 step installation procedure.
  o The automated check for incompatibilities (there is normally a view to tell you what will not work) is fairly deficient. I have (by mistake) tested on a schema with lots of (unsupported) LONGs, do you think I got any warning?
  o Although a surprisingly high number of DDL commands are successfully replicated (including CREATE USER, etc), others are understandably not replicated (when you extend a tablespace - well the directory lay-out may be different, so it makes sense. The workaround is to have AUTOEXTEND ON, which I am usually reluctant to have), something as mundane as RENAME is not - with all the ensuing consequences you may imagine.
  o I have found no way to ensure that the time gap between the two databases stayed below some predefined threshold. Not sure that issuing regular ALTER SYSTEM SWITCH LOGFILE on the master is enough.

I wanted to test the performance impact of logical standby by running an import, first without it, then with it, and also to measure how fast the copy was catching up, but I've given up my tests after a few ORA-600 errors.

The concept is great, and I am sure to have another look at it ... later.


Stephane Faroult
Oriole Software
Please see the official ORACLE-L FAQ:
Author: Stephane Faroult

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Received on Wed Nov 12 2003 - 13:14:26 CST

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