A database clone is a complete and separate copy of a database system that includes the business data , the DBMS software and any other application tiers that make up the environment. Cloning is a different kind of operation to replication and backups in that the cloned environment is both fully functional and separate in its own right. Additionally the cloned environment may be modified at its inception due to configuration changes or data subsetting.
The cloning refers to the replication of the server in order to have a backup, to upgrade the environment.
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Clone (database) Wikipedia(Text) CC BY-SA