SQL Server RUNNABLE – SUSPENDED – RUNNING status model

Some background information on the SQL Schedulers , will make understanding the RUNNABLE – SUSPENDED – RUNNING  model clearer.

This leads us into the RUNNABLE – SUSPENDED – RUNNING 

1)      RUNNING – thread is executing on the server

2)      SUSPENDED – thread is waiting for resources to become available.

3)      RUNNABLE – the thread is waiting to execute on the processor

Why does RUNNING transition to SUSPENDED ? Thread is executing and if waiting for a resource moves to SUSPENDED into the waiter list 

Why does SUSPENDED  transition into RUNNABLE? The resource is now available and moves to the bottom of the RUNNABLE queue. 

Why does RUNNABLE transition into RUNNING?  Top spid at head of RUNNABLE queue moves to processor