All these are to tell android system what to do if the service is got 'killed'
As you know, there are lots of services keep running in the background and they will consume some memory. For simplicity, under 2 situation will the services being terminated:
- When our device memory goes down to a critical level it will automatically start terminating services to release memory.
- Users manually stopped the services (Oh! I find you the invisible memory killer!! Go to die!!! .\ /. )
