DBA_WAITERS

DBA_WAITERS shows all the sessions that are waiting for a lock. In an Oracle RAC environment, this only applies if the waiter is on the same instance.

Column	Datatype	Description
`WAITING_SESSION`	`NUMBER`	The waiting session
`WAITING_CON_ID`	`NUMBER`	The container ID (`CON_ID`) of the waiting session
`HOLDING_SESSION`	`NUMBER`	The holding session
`HOLDING_CON_ID`	`NUMBER`	The container ID (`CON_ID`) of the holding session.
`LOCK_TYPE`	`VARCHAR2(26)`	The lock type
`MODE_HELD`	`VARCHAR2(40)`	The mode held
`MODE_REQUESTED`	`VARCHAR2(40)`	The mode requested
`LOCK_ID1`	`NUMBER`	Lock ID 1
`LOCK_ID2`	`NUMBER`	Lock ID 2