SELECT   bs.username "Blocking User", bs.username "DB User",
         ws.username "Waiting User", bs.SID "SID", ws.SID "WSID",
         bs.serial# "Serial#", bs.sql_address "address",
         bs.sql_hash_value "Sql hash", bs.program "Blocking App",
         ws.program "Waiting App", bs.machine "Blocking Machine",
         ws.machine "Waiting Machine", bs.osuser "Blocking OS User",
         ws.osuser "Waiting OS User", bs.serial# "Serial#",
         ws.serial# "WSerial#",

         DECODE (wk.TYPE,
                 'MR', 'Media Recovery',
                 'RT', 'Redo Thread',
                 'UN', 'USER Name',
                 'TX', 'Transaction',
                 'TM', 'DML',
                 'UL', 'PL/SQL USER LOCK',
                 'DX', 'Distributed Xaction',
                 'CF', 'Control FILE',
                 'IS', 'Instance State',
                 'FS', 'FILE SET',
                 'IR', 'Instance Recovery',
                 'ST', 'Disk SPACE Transaction',
                 'TS', 'Temp Segment',
                 'IV', 'Library Cache Invalidation', 
                 'LS', 'LOG START OR Switch',
                 'RW', 'ROW Wait',
                 'SQ', 'Sequence Number',
                 'TE', 'Extend TABLE',
                 'TT', 'Temp TABLE',
                 wk.TYPE ) lock_type,
         DECODE (hk.lmode,
                 0, 'None',
                 1, 'NULL',
                 2, 'ROW-S (SS)',
                 3, 'ROW-X (SX)',
                 4, 'SHARE', 
                 5, 'S/ROW-X (SSX)',
                 6, 'EXCLUSIVE',
                 TO_CHAR (hk.lmode)
                ) mode_held,
         DECODE (wk.request,
                 0, 'None',
                 1, 'NULL', 
                 2, 'ROW-S (SS)',
                 3, 'ROW-X (SX)',
                 4, 'SHARE', 
                 5, 'S/ROW-X (SSX)',
                 6, 'EXCLUSIVE',
                 TO_CHAR (wk.request)
                ) mode_requested,
         TO_CHAR (hk.id1) lock_id1, TO_CHAR (hk.id2) lock_id2,
         DECODE
            (hk.BLOCK,
             0, 'NOT Blocking',         /**//* Not blocking any other processes */
             1, 'Blocking',             /**//* This lock blocks other processes */
             2, 'Global',          /**//* This lock is global, so we can't tell */
             TO_CHAR (hk.BLOCK)
            ) blocking_others
    FROM v$lock hk, v$session bs, v$lock wk, v$session ws
   WHERE hk.BLOCK = 1
     AND hk.lmode != 0
     AND hk.lmode != 1
     AND wk.request != 0
     AND wk.TYPE(+) = hk.TYPE
     AND wk.id1(+) = hk.id1
     AND wk.id2(+) = hk.id2
     AND hk.SID = bs.SID(+)
     AND wk.SID = ws.SID(+)
     AND (bs.username IS NOT NULL)
     AND (bs.username <> 'SYSTEM')
     AND (bs.username <> 'SYS')
ORDER BY 1;

简化版本的：

SELECT   SID, DECODE (BLOCK, 0, 'NO', 'YES') blocker,
         DECODE (request, 0, 'NO', 'YES') waiter
    FROM v$lock
   WHERE request > 0 OR BLOCK > 0
ORDER BY BLOCK DESC;