Incremental backup only copies those Oracle blocks modified since a previous incremental backup (level <= n)

Cumulative backup copies all Oracle blocks changed since the previous backup at a level less than n (level < n)

and there arent 3 levels only, you can define up to 5 (0 to 4)

considering we are using incremental-cumulative backup:
if I have a level 0 backup on Sunday, a level 1 backup on Tuesday, and on Wednesday I have a level 2 backup then on Wednesday I will copy changed blocks since Tuesday, if on Thursday I have a level 1 backup I will be copying changed blocks since level 0 since level 0 < level 1, look like this

Sunday level 0
Tuesday level 1
Wednesday level 2
Thursday level 1

We are on Thursday, previous backup level is 2, is Thursday level 1 less than 2? No so go another day back, is Tuesday backup level less than 1? No so go back again, is level 0 less than 1? YES! So we backup all changed blocks since level 0


if we were using incremental backup it will be like this

Sunday level 0
Tuesday level 1
Wednesday level 2
Thursday level 1

On Wednesday I will be copying changed blocks since Tuesday since level 1 <= level 2
On Thursday I will be copying changed blocks since Tuesday since level 1 <= level 1

All these incremental backup business is not complicated just think:

my current backup level has to be BIGGER OR EQUAL to last backup level if I want to perform incremental backup

current backup level >= last backup level =====> incremental

my current backup level has to be BIGGER to last backup level if I want to perform incremental backup

current backup level > last backup level =====> cumulative

[Edited by pando on 10-01-2002 at 06:42 AM]