There can never too many articles with good nmap examples.
Many thanks to Anish Shaikh for compiling his A Simple Guide to Nmap Usage.
Looking to see if the ports needed to communicate with an Oracle Enteprise Management server can be reached from the target host:
nmap -sT -P0 -p 4889-4897,1159,4898-4908 grid.example.com
Check to make sure the EM agent on the target can be reached from the management server:
nmap -sT -P0 -p 3872,1830-1849 target.example.com
Note: Diagram (for v10g) showing ports used by Oracle’s Entprise Managment can be found here.