Data Director allows you to clone databases and supports several clone types with different contents, storage requirements, and performance characteristics.

You can create different types of clones depending on whether you need schema only, schema and data, full database clones, or clones that take advantage of the linked clone technology. You can also create a clone that includes neither schema nor data but includes the database settings and backup settings.

If you create a schema only clone, none of the data in your database is cloned. If you create a schema and data clone, the complete set of schema and data is included in the clone. In that case, you might have to run a script over the clone to remove confidential data.

You can also clone only the configuration. In that case, the clone includes neither the schema nor the data.

When administrators clone a database they can choose a full database clone or a linked database clone.

Full Database Clones

A full database clone is a complete copy of the source database. Full clones allow you to isolate the source and the clone. The isolation might be useful, for example, if the source database cannot tolerate any performance degradation. Creating a full clone is typically more time consuming than creating a linked clone.

Full Database Clone
The full database clone is a precise copy of the existing database.

Linked Clones

Linked clones are two or more databases that share storage. The linked clone technology supports efficient sharing of duplicate data. Linked clones use delta disk backings. A delta disk backing is a virtual disk file that is located on top of a standard virtual disk backing file. When one of the databases writes to disk, the data is written to that database's delta disk. When one of the databases reads from disk, the read process first checks the delta disk. If the data is not in the delta disk, the database retrieves the information from the parent disk.

You can create a linked clone from a snapshot or from the current running point but not from an earlier backup or from a specific point in the past. If you use linked clones, the clone and the source database cannot change data disk size.

Linked Database Clone
Linked database clones use delta disks. The staging database has three linked clones, dev, QA, and perf. Each has its own delta disk that tracks the changes.

To choose the clone type most appropriate for your situation, consider these points:

Full clones require a longer time to create than linked clones.

Linked clones are much faster to create.

Linked clones do not support storage isolation. Having several linked clones can affect the performance of the source database and the performance of the linked clones.

VMware best practice is to first create a full clone of a production database to use it as a staging clone. Next, you create linked clones of the production system full clone, the staging system in the illustration. In this scenario, potential performance degradation affects only the staging system clone and not the production database.

Using a Full Clone as a Staging Clone
A full clone of a production database is used as a staging clone. Linked clones of the staging clone can be used for development and testing.