Global Lock

Global locks are created for sets of global supervisory functions that have minimal interaction among them. There are separate global lock for dispatcher, storage manager, I/O and a miscellaneous functions. 

Global locks are larger disabled spin lock (vs local lock is enabled spin lock). The holder of the lock will disabled interrupt  the waiter of the lock will be spinning enabled for interrupter (external interrupt). Even page fault is disabled when holding the global lock  

I/O and storage manager covers a vast area of functions. Thus they sub-divide their area into multiple locks 

Cross memory service locks is a global lock that holder can be run in enabled state. 

Both global and local lock owner cannot issue SVC.