Events (the results of) won't be send to the OMS since the agent is down. But you can make an OMS to the target database connection through sql*net (NETx) or EZconnect, don't known exactly, to see for example tablespace usage (and add a datafile) or for real time monitoring. So, if you mean by monitoring I can see what is going on in my database? Yes, that is possible. You can see the connections in the target database by using TOAD or SQL (in V$Session).
