Hi,

My Oracle version :
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.2.0 - 64bit Production
With the Partitioning, Real Application Clusters, OLAP and Data Mining options

When I am quering the v$seesion, it shows some Blocking_sessions in Blocking_sessions column.
But when I try to locate that Blocking_session through SID column,
Some time I am not able to see record of that SID whereas some times it shows that SID.

If I see that from Oracle Enterprise Manager database control, I am able to see the list
of blocking sessions with some other SID.

For Example :
If I fire the following query, it shows only one row where as it should also show me a
seesion of SID 520 also.

Code:
select SID, SERIAL#, machine, USERNAME, status, BLOCKING_SESSION
from v$session where BLOCKING_SESSION IS NOT NULL
UNION ALL
select A.SID, A.SERIAL#, A.machine, A.USERNAME, A.status, A.BLOCKING_SESSION
from v$session A, V$SESSION b WHERE A.SID=B.BLOCKING_SESSION
order by machine, status;


       SID    SERIAL# MACHINE            USERNAME   STATUS  BLOCKING_SESSION 
---------- ---------- -----------------  ---------- ------- ---------------- 
       490       2738 nitappsun04-zone1  MYSUN_NI   ACTIVE               520 

1 row selected.
I am not able to see the SID 520 here. Can I have some pointers for this.

Thanks & Regards
Arun Tayal