In ITIL 2011 Service operation paragraph 18.104.22.168 headed Major Incidents or MI, it says there is a separate procedure and you must agree what constitutes a MI. There should be a separate team, and incidents and problems should be kept separate. It is difficult to define a MI, but procedures must be put in place and clearly defined. One could consider a Major Incident a case of emergency, so the normal methods of problem management aren’t going to be enough. It isn’t quite a disaster, but it is beyond a normal incident.
You can begin by deciding who is in charge of declaring a MI. Case Management is very important and there needs to be a standard approach. There should be set guidelines, roles, and responsibilities. Skills can differ for each person. The person that is the Incident Manager may not always be the Major Incident Manager. This is why structure is important. People shouldn’t be left to make last minute decisions.
Once you have guidelines and roles in place, you should rehearse with staff to ensure everyone knows their role and duties. It is a good idea to have two teams: incident resolution and problem resolution. Impacted customers must be managed along with the restoring of service. Many companies will wait until something happens, but that leaves you frantic and unprepared. Places with several Major Incidents often practice MIM (Major Incident Management)frequently. The more you practice, the more prepared you will be in the even of a MI.