The vCenter Server Appliance requires a database to store and organize server data.
Each vCenter Server Appliance instance must have its own database. You can use the bundled PostgreSQL database that is included in the vCenter Server Appliance, which supports up to 1,000 hosts and 10,000 virtual machines.
For external databases, the vCenter Server Appliance supports only Oracle databases. These Oracle databases are of the same versions shown in the VMware Product Interoperability Matrix for the version of the vCenter Server that you are installing. See the VMware Product Interoperability Matrix at http://www.vmware.com/resources/compatibility/sim/interop_matrix.php.
If you want to use an external database, make sure that you create a 64-bit DSN so that vCenter Server can connect to the Oracle database.