12c OCI Client Issue: Remote "connect time" performance problem or delay of 9 to 10 seconds

The 12c client has event notifications enabled by default.  The client will try to reach out to the ONS (Oracle Notification Service) when it tries to

establish a connection.

If the ONS is not running or not reachable, the client might exhibit a 9-10 second delay in establishing a connection.  This is typically an OCI or

SQL*Plus client that connects via the listener or from a remote machine.

See the following document for a test that involves using the oraaccess.xml file to 'de subscribe' to the ONS.  If this eliminates the delay at

connect time, the problem is likely with the client's ability to reach the ONS service.