Oracle Hanging System

When there is an issue with an instance or session hang run this sql

sqlplus ‘/ as sysdba’
oradebug setmypid
oradebug unlimit
oradebug setinst all
oradebug -g all hanganalyze 4 <=== Issue command 3 times one minute apart
oradebug -g all dump systemstate 267 <=== Issue command 3 times one minute apart
quit

help is available :

sql> oradebug help

Trace files will be produced in the user_dump_dest directory. They are named according to the SPID of the process where the oradebug command is executed.

SQL> sho parameter user_dump_dest

NAME                                 TYPE                             VALUE
------------------------------------ -------------------------------- ------------------------------
user_dump_dest                       string                           C:\oracle\diag\rdbms\xxx\xxx1\trace
C:\Temp>set ORACLE_SID=xxxa1

C:\Temp>sqlplus / as sysdba

SQL*Plus: Release 11.1.0.7.0 - Production on Thu Aug 26 08:43:27 2010

Copyright (c) 1982, 2008, Oracle.  All rights reserved.

Connected to:
Oracle Database 11g Release 11.1.0.7.0 - 64bit Production
With the Real Application Clusters option

SQL> set timing on
SQL> set time on
08:43:38 SQL> spool oradebug_xxxx1
08:43:40 SQL> oradebug setmypid