Identifying the blocking Lock

Question

In one of our production DB we are experiencing huge bottlenecks due to locks. I am using OEM lock monitor to detect and identify the problematic lock. I am trying this out randomly as OEM list all the blocking locks. . Most times I am not able to analyse the problematic locks because of support calls from production. I just have time to kill the sessions and get the platform ready. Is there a script that I can use to identify the session that is blocking other sessions ? How do we do analysis during situations like this? At least I am interested in finding the root cause of the problem so we request the developers to fix it.
- BMP

Answer 1

&1 --><sid of any session>.if the sid provided is waiting for other sessions, it will show you the blocking session id.
Try this one (Not tested):
SELECT bs.username "Blocking User", bs.username "DB User",
ws.username "Waiting User", bs.SID "SID", ws.SID "WSID",
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#",
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
FROM Gv$lock hk, v$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')