# Replication (unidirectional or bidirectional)

Unidirectional: data committed to the sources is exactly copied to a similar database (of storage type).

Bidirectional: changes made on a copy of database are replicated on another copy of the same database and the changes of this second copy are replicated to the first copy. For more information, see [Configuring bidirectional replications](https://help.qlik.com/talend/r/en-US/7.3/change-data-capture-installation-guide/bidirectional-replications).