Are they same? Well let’s have a look on the above activities that helps in finding the differences between them.
What is a Database Clone?
* A database clone is an activity/procedure which is performed by every DBA on regular basis or when there is a requirement or request to do so from the different departments i.e. Test/Development teams.
* Cloning is nothing but creating a copy of production system in to a test or development environment. i.e. Having an exact image of production database in test area.
* Cloning is a procedure for preparing and creating a test or development servers with the copy of Oracle production database for testing upgrades, migrating an existing system to new hardware.
* A cloning process includes a copy of Oracle Home (Directories and Binaries) backup and Database (Database related files) backup to prepare the instance on another server.
* Though, it is possible to clone a database on the same server, Oracle doesn’t suggest to clone a database on the same server, where the production database is running.
What is a Database Refresh?
* A Database Refresh is also referred to as a database clone. However, we don’t clone Oracle Home rather we clone the Database as refresh.
* Refreshing a database is something like applying the changes or updates of production database to the database where the database is already cloned. i.e. let’s say you have cloned a database a month back, and now you are asked for doing refresh of a database, then you will perform the backup of database and prepare the clone the instance again on test server. This is nothing but refreshing.
* Refreshing of a particular table, group of tables, schema, or tablespace will be done using traditional export/import, transportable Tablespaces, or data pump methods.
* When an Oracle patch is applied on Production System, or in doubt, you have to prepare and clone the database again with the copy of Oracle Home (Directories and Binaries) Backup and Database (Database related files) Backup to prepare the instance.
* The difference between Cloning and Refreshing is that cloning process includes Oracle Home and database Clone; where as Refreshing process only includes database clone.
* If seen, the words, Clone and Refresh are used interchangeably for the sake of convenient.
When and why we Clone a Database?
* Generally production (PROD) database is cloned for various reasons and needs i.e. for something to be tested or something to be developed later those to be moved to production.
* It’s normal and quite common thing is that whenever there is any change or update to be performed and do not know the impact or effect after applying it on production (PROD), it’s required to be applied and tested on *NON* production database first (TEST or DEV), after the confirmation of change success, given by the users, then the changes will be moved to production.
* A Cloned test instance (TEST) for testing team/environment is exclusively used for testing the changes or issues which will become severe on Production. Oracle Support gives the solution as fix when there is an issue in the database, so this fix needs to perform or apply on test/development databases.
* A Cloned development instance (DEV) for development team/environment is used for developing the new changes and then deploying the same on Production.
* A Cloned patch instance is used for patching to know the impact and the time required to apply the same on Production.
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