Diff Between RMAN full backup & level 0 backup

Diff Between RMAN full backup & level 0 backup
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A level 0 incremental backup, which is the base for subsequent
incremental backups, copies all blocks containing data, backing the
datafile up into a backup set just as a full backup would.
The only difference between a level 0 incremental backup and a full
backup is that a full backup is never included in an incremental
strategy
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OR

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A level 0 incremental backup, which is the base for subsequent
incremental backups, copies all blocks containing data. The only
difference between a level 0 backup and a full backup is that a full
backup is never included in an incremental strategy.

If no level 0 backup exists when you run a level 1 or higher backup,
RMAN makes a level 0 backup automatically to serve as the base.

The benefit of performing multilevel incremental backups is that RMAN
does not back up all block all of the time.

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Block Corruption & Recovery By RMAN

A corrupt block is a block that has been changed so that it differs from what Oracle Database expects to find.

Each Oracle data block is written in a proprietary binary format. Before an Oracle data block is used, Oracle checks it for possible block corruption. A block corruption is considered to exist if the format of the data block doesn’t conform to its format

Cause For Block Corruption

An Oracle database can become corrupt for various reasons, such as these:
– OS bugs causing bad reads or bad writes.
– Hardware issues.
- Oracle Bug.
- Non-Oracle program attaching and illegally writing to the same shared memory address space.

Recovery with RMAN
Multi block corrupted:BLOCKRECOVER DATAFILE BLOCK DATAFILE BLOCK block#>;

Single block corruption:BLOCKRECOVER DATAFILE BLOCK ;

Corrupt blocks can be identified using:

Error messages
The alert log
Trace files
The dbverify utility
The new view V$DATABASE_BLOCK_CORRUPTION lists corrupt blocks in the database detected during the backup operation. Recovered blocks will still be listed until the next backup is performed.

to check a database for both physically and logically corrupt blocks.Here is the syntax:RMAN> backup validate check logical database;

RMAN does not physically backup the database with this command but it reads all blocks and checks for corruptions.If it finds corrupted blocks it will place the information about the corruption into a view: v$database_block_corruption

Master Note for Handling Oracle Database Corruption Issues (Doc ID 1088018.1)
Master Note For Oracle Recovery Manager (RMAN) (Doc ID 1116484.1)
RMAN : Block-Level Media Recovery – Concept & Example (Doc ID 144911.1)
How To Use RMAN To Check For Logical & Physical Database Corruption (Doc ID 283053.1)

Creating an RMAN Database User on the Target Database for Backups

By default, when RMAN logs into the target database, it does so as the SYS account (as SYSDBA) without any configuration required. This is commonly not what you would want to do in a production system. It is recommended that you create specific database accounts to be used just for RMAN backup purposes. Before going in to the details of how to do this, lets first look at how to log in using the default SYS account:

Login as oracle user

Oracle@rhel5 : rman target /

The above command will login to the target database (TARGDB) using the SYS account (as SYSDBA).

Now, let’s go ahead and create the database user that will be used for all RMAN backups:

% sqlplus “/ as sysdba”

SQL> CREATE USER Rman_user IDENTIFIED BY Rman_user
2 DEFAULT TABLESPACE users TEMPORARY TABLESPACE temp;

SQL> GRANT sysdba TO Rman_user;

After creating the RMAN backup user, you can now login to the target database using the following:

% rman target Rman_user/Rman_user

Notice that the above command will login to the target database (in this case, whatever database is set by the ORACLE_SID environment variable) using SYSDBA privileges. We do not have to specify the “as sysdba” clause when logging into RMAN; it is assumed and RMAN will always use SYSDBA privileges.

Note : now RMAN is in no catalog mode and Control file will be used for the resgistering backup.

Thanks
L N REDDY