Global enqueue process LCK0 hangs causing ORA-29770 error and instance crash

Learn more about Oracle DB internals from MOS document "ORA-29770: Global Enqueue Process LCK0 .. Is Hung For More Than 70 Seconds" in note ID 2020465.1 so you can understand how PMON holds up other processes and what kind of wait events or DB log events that you need to be on the lookout for before your instance crashes!