Recoverable RMAN Image Copies.

This feature is available from Oracle 10g onwards. This is a very nice feature that can reduce the time of the recovery to a great extent.

Image copies are not new to Oracle but recoverable copies are for sure.

In Oracle there are generally two types of backups available

a) Full database backups. (Level 0 backups)

b) Incremental backups (eg Level 1 backups)

For having incremental backups, we need to have a full backup of the database. Once we have full backup of the database, we can have incremental backups after that reducing the amount of time and space involved in the backup operation.

So, whats new with the “Recoverable Image Copies”?

This is a feature in which image copies of the database file will be getting updated with the new changes in the database using Incremental backups.

As we know that image copies are same as our datafiles and same as we take a copy of datafile using Os command with only difference is that they are in RMAN format so better managed by Oracle.

SO coming to the feature, if you take a image copy of say datafile 3 today and there is an incremental backup occurring every day, now you are having an option to update the datafile 3 copy with latest changes that have happened in database using the latest incremental backup.

Lets do a small demo explaining this feature..

Brief description about the demo

I will create a tablespace and will create a table in that tablespace. We will then have a full database backup and an image copy of the database which will also include the new tablespace.

Then we will make changes to the newly created table and have an incremental backup capturing those changes.

We will update the image copy taken in the step 1 using the incremental backups.

Then we will be dropping the datafile of the new tablespace and will perform a recovery of that datafile using the image copy.

So here we start….

Start with creating a new tablespace say “test_tb” with one datafile.

[code]

Enter user-name: / as sysdba

Connected to:Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 – Production

With the Partitioning, OLAP and Data Mining options

SQL> select name from v$tablespace;

NAME

——————————

SYSTEM

UNDOTBS1

SYSAUX

USERS

TEMP

APEX

FLOW_1050410553792418

7 rows selected.

SQL> select name from v$datafile;

NAME

——————————————————————————–

D:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL\SYSTEM01.DBF

D:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL\UNDOTBS01.DBF

D:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL\SYSAUX01.DBF

D:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL\USERS01.DBF

D:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL\APEX01.DBF

D:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL\FLOW_1050410553792418.DBF

6 rows selected.

SQL> create tablespace test_tb datafile ‘D:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL\test_tb01.dbf’ size 100m;

Tablespace created.

Now we will create a table in this newly creates tablespace

SQL> create table emp_test tablespace test_tb as select * from scott.emp;

Table created.

SQL> select count(*) from emp_test;

COUNT(*)

———-

[/code]

Now we will take a full database backup using new backup command.

[code]

RMAN> backup incremental level 1 for recover of copy tag ‘test_tb_incr’ database;

Starting backup at 10-SEP-10

using channel ORA_DISK_1

no parent backup or copy of datafile 1 found

no parent backup or copy of datafile 3 found

no parent backup or copy of datafile 2 found

no parent backup or copy of datafile 5 found

no parent backup or copy of datafile 6 found

no parent backup or copy of datafile 7 found

no parent backup or copy of datafile 4 found