Closed
Description
After reading
https://dba.stackexchange.com/questions/110819/oracle-intermittently-throws-ora-12516-tnslistener-could-not-find-available-h
I suspect this is because the TNS-Listener takes some time to take note of closed connections, thus overestimating the number of open connections.
This seems likely when connections are opened and closed in rapid succession as is the case with tests.