Hi
CCMS custom metrics only for very specific MTES like emails, spool queue. For RFC availablity monitoring we have dedicated standard functionality available, you nt required to go via custom
try -> solman_setup-> Technical monitoring -> connectivity monitoring http://help.sap.com/saphelp_sm71_sp01/helpdata/en/82/33df9df04c465bad6fa4c96a7c3c62/content.htm
Please check.
Thanks
Jansi