DBA_WAITERS shows all the sessions that are waiting for a lock.
| Column | Datatype | NULL | Description | 
|---|---|---|---|
| WAITING_SESSION | NUMBER | The waiting session | |
| HOLDING_SESSION | NUMBER | 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 | VARCHAR2(40) | Lock ID 1 | |
| LOCK_ID2 | VARCHAR2(40) | Lock ID 2 |