The mc_long_msg cannot be changed in TSAVM 11.3.01.
There is an existing RFE for same.
Below is the RFE –
RFE – DRTEA27

For mc_host – Below are the changes and the justifications for changing the slots –

mc_host varies in the way it is being used. By its original definition, it should contain the qualified name of the host on which the problem occurred. For synthetic monitoring, the problem is manifested at the agent (simulating real end-user in a location). However, when moving to the new metric rules in 11.3, an event can be due to problems in many locations (i.e. at 75% of the locations). Since we could not populate the slot with multiple entries representing the impacted locations (agents), we decided to set the mc_host_x slots with the portal details, which is the component that manages the events.

* mc_host
--- 10.7 TEA Agent Host Name
--- 11.3 Portal Host Name

* mc_host_address
--- 10.7 TEA Agent IP address
--- 11.3 Portal IP address

* mc_host_class
--- 10.7 TEA Agent version and build number
--- 11.3 Portal Version