How to configure a listener for a separate ENV?-Standalone Only
Occasionally it is necessary to configure 2 distinct Oracle net or sqlnet environments for the same database or instance.
If it is necessary for some clients to reference a sqlnet.ora file that is different or uniquely configured, we can accomplish
this by configuring a separate listener using a statically defined SID_DESC where the ENVS or environment setting points
to a sqlnet.ora file that is different from the dynamically registered service.
Here's an example. Customer needs to use both SSL (TLS) and Native encryption at the same instance. This can not be configured
in a single sqlnet.ora file so a separate listener is necessary. In this case, we've configured a listener.ora file for a PDB that points