VM migrations are triggered inside the data center, by an internal data center event. Therefore, triggering a migration means receiving and processing a VM_MIGRATION event:

send(this.getId(),delay,CloudSimTags.VM_MIGRATE,vm);

The delay field contains the estimated migration completion time. Therefore, when using it, the method that starts the migration process has to provide estimated completion time. After the delay, the event is received by the data center, which is interpreted as migration completed: therefore, from this time on the VM is available in the destination host.

can u tell me .....how do i know policy used in Migration whether it Pre-copy or Post Copy.................where is the code for this policy in Cloudsim........

Please tell me...........