Responsible for jacking into the NEBCALLBACK_* calls and send them to a socket. If the socket is not available the events are written to a backlog and sent when the socket is available again.
The Merlin daemon listens to the socket that merlin-mod writes to and sends all events received either to a database of your choice (using libdbi) or to another merlin daemon. If the daemon is unsuccessful in this it writes to a backlog and sends the data later.
This is a database that includes Naemon object status and status changes. It also contains comments, scheduled downtime etc.