As @lamw documented in his blog, you can access the database in the vCenter software appliance (vCSA). In the first appliance of version 5.0, VMware included IBM DB2 Embedded and then switched to vPostgres right after. That’s because vPostgres is VMware’s own product based on the open source Postgres.
By default, the access to the vPostgress database is limited to local applications. In other words, if you want to access the database remotely, it will not work. After researching a little, I figured out how to configure the databse for remote access.