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Re: What is the different between incremental and cumulative export ?

From: Pete Sharman <psharman_at_us.oracle.com>
Date: Tue, 11 Jan 2000 08:39:27 -0800
Message-ID: <387B5CBF.81BF2E6E@us.oracle.com>


Your header and your text ask two different questions so I'll try to answer both:

  1. The export utility allows you to perform three levels of export - complete (everything), cumulative (all tables that have changed since the last cumulative or complete export) and incremental (all tables changed since the last export, regardless of what the level was).

Theoretically, what this meant was you could set up an export regime where you could do complete exports once a month, cumulative exports once a week, and incremental exports each night, thus allowing smaller and faster exports.

The problem was (and still is by the way) that the way export determined whether a table had changed was by looking at some exp views created by catexp.sql. These views are populated with information when a table changes, so you might find that EMP had changed but not DEPT. What is counted as a change is ANY data change. So for example, you could have a 50 million row table with one row changed. The exp views would be populated to say the table had changed, and the next export would export the ENTIRE table, not just the row that was changed.

The result is that incremental and cumulative exports were virtually useless. I believe they are not being enhanced at all, and they may go away in a later release, but I haven't seen that officially confirmed (personal opinion, yadda yadda yadda).

2. There is since Oracle8 with the RMAN utility the ability to do backups of the data files that allow you to say I only want the blocks that have changed. From memory, you can have 10 levels of backup with RMAN, so it's really what allows the functionality you're after without the overhead.

HTH. Pete

yewpc_at_rnd.celcom.com.my wrote:

> Can anyone tell me what is the different between incremental and
> cumulative backup ?
> Thank you
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.


Received on Tue Jan 11 2000 - 10:39:27 CST

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