For the Service Registry, it is one of the main components of its Server part used to store registry data. For the XACML, it is used as XACML Registry to deploy, retrieve, and delete XACML policies. For the Auxiliary Storage, the repository is used to store Request/Callback context.
Jackrabbit supports two types of storage: file and database. By default, the file type is used, but you can change it to the database type. When the database type of storage is used, by default, an embedded Apache Derby DB is configured. This appendix describes how to configure Apache Jackrabbit with another database, for example: Postgres and Oracle.