Do you need a license server to manage ESX4.0/i ?
=> You no longer need license server to manage ESX4.0/i but you will need it for managing ESX3.x systems.
What happens when license expires?
=> There are two types of licenses. one is vCenter license and other is vSphere license
When vCenter license expires, hosts gets disconnected from vCenter. But you can still power on and reset virtual machines You can also access vSphere host directly using vSphere client.
And when vSphere license expires, you cannot power on or or reset virtual machine.
What is the role of ADAM in vCenter linked mode?
ADAM (Active directory in application mode) is used to synchronize data across multiple data centers. ADAM is installed as part of vCenter installation.ADAM on each vCenter instances stores data i.e. roles and licenses of every other vCenter in linked mode group and keep replicating each other over a period interval. Due to this replication cycle, each instance of vCenter must have right time. They should not be 5 mins apart from each other
Does restart is needed if you join vCenter instance to linked mode group?
yes – But it is not confirmed if service or server needs restarts and, Also when the system is removed from linked mode does it again needs to restarts
In Linked mode how roles are affected ?
when two systems with same role and same privileges are available, both these roles are combined into single role. If there is conflict in role but different privileges then conflict must be resolved automatically or manually.