iHub stores information related to users, roles, groups, files and folders, or metadata, in a third-party relational database management system (RDBMS). By default, iHub uses the PostgreSQL RDBMS for this purpose. iHub also supports the use of an Oracle, DB2, and SQLServer database.

A database can contain one or more schemas. An Encyclopedia volume schema can relate to one or more volumes. When installing BIRT iHub with either the OOTB PostgreSQL or a third-party database, the install program creates two schemas, one for Encyclopedia metadata, and one for the system metadata. In Advanced view of Configuration Console, on Volumes, the metadata database appears in the first column, the schemas the database contains appear in the second column, and the volume the Encyclopedia volume schema relates to appears in the third column, as shown in Figure 2‑8.