Content management systems need to manage both content and metadata. EMC Documentum uses the host file system (by default) to store the content and a database to manage metadata and its association with the content items. Note that the content can also be stored in other types of storage systems, including a Relational Dababase Management System (RDBMS), a content-addressed storage (CAS), or external storage devices.
Note
EMC coined the term content-addressed storage (CAS) in 2002 when it released its Centera product. CAS provides a digital fingerprint for a stored content item. The fingerprint (also known as an ID or logical address) ensures that it is exactly the same item that was saved. No duplicates are ever stored in CAS.
A repository is a managed unit of content and metadata storage and includes areas on the file system and a database. However, the details of the organization of the files and metadata in a repository are hidden from the users and applications that need to interact with the repository. The repository is managed and made available to the users and applications via standard interfaces by a Content Server process. The following figure shows the basic structure of a repository:
The repository was known as docbase in pre-5.3 versions of the Documentum platform. These two terms are used interchangeably by the Documentum community.