Oracle Database Discussions

Hi,

I am confused that whether incremental backup is possible when the database is in noarchivelog mode. I experimented on it but got even more confused.

My test database was in noarchivelog mode. First I cleanly shutdown the database and started it at mount stage. Then from RMAN I took a full database backup. The full database backup set was of size 6 GB.

Then I altered the database to open stage and some data inserted. After that the database was kept in mount stage.

Now from the RMAN I tried incremental backup. For which I executed this syntax.

RMAN> backup incremental level 1 database;

This executed successfully. But when I checked this incremental backup set, the size was 6.1 GB.

When I checked the same thing keeping the database in archivelog mode, the backup set size corresponding to incremental backup was observed to be just 20MB.

But things stared to get more confusing as I tried to repeat the whole thing. I turned the database into noarchivelog mode. And by executing archive log list I was confirmed of the database mode.

Again I took one full backup keeping the database in mount state. The backup set size was 6.1 GB. Then I opened the database and inserted some rows. This time when I took an incremental backup at level 1 the backup set for the same showed just 10MB.

For all the scenarios I tried with the same syntaxes. The database version is 10.2.0.3 and platform is Solaris 10.

I would be really grateful if someone can explain why such thing happened. One more thing that I want to know is that how Oracle check out which blocks were modified after last full backup.

Thanks in advance