What is a Cloning?

Cloning is a process to create an exact copy of oracle database without using export/import. This method is used by DBAs to update test or development environments from production.

In cloning process, we will copy the datafiles from our production database and use it to create your test database. So your test database will be a mirror image of the production in all respects, except of course, for the database name. We will be changing that.

We can create clone instance/ database on our production server as well as different server but as per my recommendation we should not be done on our production server.

Why Export/import is not suitable for Cloning?

Export/Import process is very bulky if you want to use export / import you have to do the data refresh frequently and import takes a long time if your database is of good size.   You can of course, resort to exporting and importing tablespaces if they are self contained and you are running version 8i or greater, enterprise edition. A faster alternative is to clone the database.

Method behind the Cloning?

The method used here is actually a backup/recovery of the production database on the test server. We just recreate the controlfile on the test machine using a new database name and do a recovery. The datafiles from the production database can be from a hot backup, a cold backup or an RMAN backup. If the database was open during backup (hot or RMAN), you will need all the archivelogs since the time the backup started to recover the database to its present state (that is, do a complete recovery). Throughout the article, I will refer to environment variables by their UNIX notation (example $ORACLE_HOME). Replace this with the Windows equivalent if you are using NT/2000 (example $ORACLE_HOME becomes %ORACLE_HOME%).

Reason for Cloning?

In every oracle development and production environment there will become the need to transport the entire database from one physical machine to another.   This copy may be used for development, production testing, beta testing, etc, but rest assured that this need will arise and management will ask you to perform this task quickly. 

Steps involve in cloning?

1.  Relocating an Oracle database to another machine or Relocation a datfile to different mount point if you want to clone in same production machine.

2.  Moving Oracle database to new Storage media.

3.  Renaming Oracle database.

Difference between cloning and Refreshing ?

A Cloning process includes a copy of Oracle Home (Binaries) and Database files backup to prepare the instance on Another Server.

A Database refresh is referring to as a database clone. However, we don’t clone Oracle Home only we clone the database as refresh.

The difference between cloning and refreshing is that clone process include Oracle Home and Database, where as refreshing process only include database clone.