Service migration is a process of copying or moving a service and it's state from one grid node to other. If target node already has the same service but different version it will be upgraded (theoretically, downgrade is also possible).

Service migration mechanism makes it possible to run services where they are needed. For example, if a service was not deployed on a node and user tries to invoke it - the request will be routed to a node which has the service deployed. At the same time, the node will realize that it makes sense to migrate the service to it in order to enhance performance. This situation often happens when a new node is connected to the grid and but does not have all useful services deployed yet. Similarly, node can decide to undeploy a service if it is not used and it will use service migration if the service needs to be used again.

Service migration is also used when a services needs to be upgraded to later version. Whenever a node in a grid gets a new version of the service (by on-line update or manual upload via service management console) latest version of the service will be propagated (migrated) to all other nodes. If some nodes are off-line they will pick up the latest service version when they are back on-line.