Installing the collector the install hangs on Validating components connectivity
connectivity issue between the middleware host and the monitored instance
Verify the following sql can be run from the middleware host, connecting to the monitored instance (subsitute actual values)...
sqlplus <user>/<password>"@(DESCRIPTION=(ADDRESS=(HOST=<host>) (PROTOCOL=tcp)(PORT=<port>)) (CONNECT_DATA=(SID=<sid>)))"
Resolve any connection issue between the middleware and monitored instance, then try the install again.