Performance Explorer provides a set of predefined data sources that are queried through SNMP. However, you can add an entry for ORADB-MIB in an SNMP datasource.
Establish a connection to a data source to query through SNMP and create an initial view that contains the measures you want to monitor.
SNMP involves an SNMP agent, which is typically provided by the application vendor. For example, Oracle databases expose data sources using their SNMP agents. The client-side counterpart is Performance Explorer, which collects performance data.