Sounds like we're mixing metricbeat and packetbeat here.
Being a proprietary disclosed protocol, the Oracle DB protocol is not supported by packetbeat.
Metricbeat on the other hand actively polls the services for it's metrics. Unfortunately adding Oracle DB support would require dynamically linking against the client libs, enforcing all users to have these libs available.
There's an old (it seems unmaintained) community beat named orabeat. Maybe one can turn this into a metricbeat module. The beats code-base adds experimental support for go based plugins, but this would also require some you to compile beats and such yourself.