Can anyone please explain me what are the contents /information available in mailbox ?
And while doing an head swap what is the need for deleting the Mailbox local ?
Solved! See The Solution
mailbox is used as secondary heartbit between controllers in HA pair as well as to keep track of which controller controls disks in case of takeover. For these purposes systemid is used. When doing head swap, systemid changes, so mailbox content becomes invalid and needs to be reinitialized.