The second paragraph in slide notes state:
The embedded database is a DB2 Express database.Correct:
The IBM DB2 Express database - originally deployed in vSphere 5.0 - has been soon replaced by PostgreSQL.
Versions 5.0.1 and 5.1 of the vCenter Server Appliance use PostgreSQL for the embedded database instead of IBM DB2, which was used in vCenter Server Appliance 5.0.Source:
vSphere 5.1 Documentation Center.