An EEM policy is an entity that defines an event and the actions to be taken when that event
occurs. There are two types of EEM policies: an applet or a script. An applet is a simple form of
policy that is defined within the CLI configuration. answer 'event manager applet ondemand
event register
action 1.0 syslog priority critical msg 'This is a message from ondemand'
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There are two ways to manually run an EEM policy. EEM usually schedules and runs policies on the
basis of an event specification that is contained within the policy itself. The event none command
allows EEM to identify an EEM policy that can be manually triggered. To run the policy, use either
the action policy command in applet configuration mode or the event manager run command
in privileged EXEC mode.
Reference:
3s-book/eem-policy-cli.html

OMP is the control protocol that is used to exchange routing, policy, and management information between Cisco vSmart Controllers and Cisco IOS XE SD-WAN devices in the overlay network. These devices automatically initiate OMP peering sessions between themselves, and the two IP end points of the OMP session are the system IP addresses of the two devices.