When a process requests an available resource
System must decide if immediate allocation leaves the system in a safe state
System is in safe state
if there exists a sequence of ALL the processes
Pi can still request by currently available resources + resources held by all the Pj, with j < i , That is:
If Pi resource needs are not immediately available then Pi can wait until all Pj have finished
When Pj is finished Pi can obtain needed resources, execute, return allocated resources, and terminate
When Pi terminates Pi +1 can obtain its needed resources and so on