"Failed to establish an Oracle JDBC connection protocol. Reason: Unknown Host" when verifying an agent connection (4295460)

When validating the connection for an Oracle agent in the administration area, verifying the connection with the message:

"Database instance: MYINSTANCE on host MYHOSTNAME, the connection to the instance failed with this error: Failed to establish an Oracle JDBC connection protocol. Reason: Unknown Host "myhostname.domain.com".. [Oracle Error Code = 17002. SQL state : 08006]."

CAUSE 1

The FglAM server cannot resolve the hostname of the monitored host.

CAUSE 2

The Oracle listener was not running on the monitored host.

CAUSE 3

An incorrect port was specified in the connection validation process or the port is blocked from the FglAM server.

RESOLUTION 1

Activate the Listener service or process on the monitored Oracle host

RESOLUTION 2

Confirm that the port used by the database agent is correct and is not blocked.

RESOLUTION 3

Use the FQDN (fully qualified domain name in the database agent installer wizard such as HOSTNAME.DOMAIN.COM)

or 

1. Connect using a remote desktop (Windows) or SSH session (Linux) to the Foglight Agent Manager where the database agent is being installed.
2. Using a command line, ping the hostname to see if it resolves.
3. If the hostname does not resolve with the hostname, ping the FQDN (fully qualified domain name).
4. Update the hosts file on the FglAM server to include the IP address, hostname, and fully qualified domain name
5. Retry adding the new database agent using the DB agent installer