Database in Begin backup mode

[sayampu]

Hi Tim,

As per my knowledge, when we put a database in "backup Mode" , datafiles headers freeze and CKPT not update the headers with latest SCN.
My doubts are:

1.In this scenario, why it generates excessive archives?
2.What is the advantage , using RMAN instead of Backup mode while hot backups?
3.Suppose i am taking hot backup using "backup mode". If the instance terminate in the middle of backup, then how can we recover(plz tell me the steps) the database.

Thanks in advance

Regards
Sayampu

[Tim...]

Hi.

1) Normally, Oracle only writes changed data into the redo logs (deltas). When the database is in backup mode, Oracle writes full copies of the blocks to the redo logs, not just changes with the block. As a result, the redo generation increases when the database is in backup mode.

2) When you use RMAN for online backups, the database doesn't have to be put into backup mode, so there is no extra redo generated. This can be massively advantageous for systems that are busy during backups.

3) Hopefully a crash will recover itself, but if not, you need to do something like this.

Code: Select all

startup mount;
recovery database;
alter database open;

Cheers

Tim...

[tonis]

Hi friends,
regarding step 2 in mr. Tim's code, it should be:

Code: Select all

recover database;

just pointing a simple grammar mistake to save google or documentation searches (not trying to be a smart ass...).

[Tim...]

Thanks for that.

Cheers

Tim...

[sayampu]

Hi tim,

Thanks for your time.

After open the database in mount state, Should we end the backup mode or automatically will it do that?

SQL>startup mount
SQL>alter database end backup; ***********(is it necessary?)
SQL>recover database; (USING backup controlfile)(supply logs if required)
SQL>alter database open resetlogs(if needed)

Thanks & regards
Sayampu

[Tim...]

Hi.

You will need to end backup mode manually.

Cheers

Tim...