A common error is 'Unable to establish the connection with the database. ORA-12541: TNS: No Listener.'
This can often occur when attempting to run the Update Readiness Tool (URT) on the Enforce server,
Error: unable to establish db connection for user protect: ORA-12541: TNS:no listener
It is possible the Listener service is not running on the Oracle Server.
To resolve the issue, follow the steps below:
Confirm the Listener service is running on the Oracle Server using the "lsnrctl status" command.
Verify the Environment variables are set correctly on the Enforce Server
Assure the destination address used matches that of the Oracle Listener
For additional information related to testing the connection string itself, Troubleshoot Enforce connection to Oracle