We’re facing the issue database frequently stop connecting after upgrade to 19c (19.3). this database which is running on windows server 2016.
Errors in listener.log file
TNS-12518: TNS:listener could not hand off client connection
TNS-12546: TNS:permission denied
TNS-12560: TNS:protocol adapter error
TNS-00516: Permission denied
64-bit Windows Error: 5: Input/output error
Core dump should created on somewhere in your database server locations.
Apply database 19.7 or latest patches. the issue will be fixed