在有些时候，我们需要通过systemstate或者hanganalyze来收集数据库hang信息，但是当我们的数据库不能登录的时候，无法通过常规手段来使用该方法来收集信息。ORACLE的开发者也考虑到了类似情况，让我们可以通过dbx或者gdb来收集数据库信息.这里我通过在linux平台上模拟一个新会话，然后通过gdb直接对该会话进行做systemstate,然后操作该会话(证明gdb操作后正常),来实现类似系统hang住，无法登陆的时候怎么做systemstate.
模拟会话
就是假设我们hang住的系统中的数据库进程(为了后面gdb和验证对会话影响而使用,不然可以直接使用oracle 后台进程来完成该操作)

[oracle@xifenfei ~]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.3.0 Production on Thu Jan 17 18:28:30 2013
Copyright (c) 1982, 2011, Oracle.  All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL>

查找数据库进程
在另外一个shell窗口找出数据库进程

[root@xifenfei trace]# ps -ef|grep LOCAL
oracle    7476  7473  0 18:28 ?        00:00:00 oracleora11g (DESCRIPTION=(LOCAL=YES)(ADDRESS=(PROTOCOL=beq)))
root      7487  7326  0 18:28 pts/2    00:00:00 grep LOCAL

gdb做systemstate

[oracle@xifenfei trace]$ gdb $ORACLE_HOME/bin/oracle 7476
GNU gdb (GDB) Red Hat Enterprise Linux (7.0.1-37.el5)
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i386-redhat-linux-gnu".
…………
Reading symbols from /u01/oracle/oracle/product/11.2.0/db_1/lib/libnque11.so...
Loaded symbols for /u01/oracle/oracle/product/11.2.0/db_1/lib/libnque11.so
0xb789c424 in __kernel_vsyscall ()
(gdb)  print ksudss(10)  <--输入print ksudss(10)
$1 = 0
(gdb) quit
A debugging session is active.
        Inferior 1 [process 7476] will be detached.
Quit anyway? (y or n) y
Detaching from program: /u01/oracle/oracle/product/11.2.0/db_1/bin/oracle, process 7476

查看trace文件

[oracle@xifenfei trace]$ ls -l *7476*.trc
-rw-r----- 1 oracle oinstall 742438 Jan 17 18:28 ora11g_ora_7476.trc
[oracle@xifenfei trace]$ more ora11g_ora_7476.trc
Trace file /u01/oracle/diag/rdbms/ora11g/ora11g/trace/ora11g_ora_7476.trc
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
ORACLE_HOME = /u01/oracle/oracle/product/11.2.0/db_1
System name:    Linux
Node name:      xifenfei
Release:        2.6.32-200.13.1.el5uek
Version:        #1 SMP Wed Jul 27 20:21:26 EDT 2011
Machine:        i686
VM name:        VMWare Version: 6
Instance name: ora11g
Redo thread mounted by this instance: 1
Oracle process number: 21
Unix process pid: 7476, image: oracle@xifenfei (TNS V1-V3)
*** 2013-01-17 18:28:59.225
*** SESSION ID:(143.23) 2013-01-17 18:28:59.225
*** CLIENT ID:() 2013-01-17 18:28:59.225
*** SERVICE NAME:(SYS$USERS) 2013-01-17 18:28:59.225
*** MODULE NAME:(sqlplus@xifenfei (TNS V1-V3)) 2013-01-17 18:28:59.225
*** ACTION NAME:() 2013-01-17 18:28:59.225
===================================================
SYSTEM STATE (level=10)  <---systemstate levle 10
------------
System global information:
     processes: base 0x32bc5b38, size 150, cleanup 0x32bd5990
     allocation: free sessions 0x32085b84, free calls (nil)
     control alloc errors: 0 (process), 0 (session), 0 (call)
     PMON latch cleanup depth: 0
     seconds since PMON's last scan for dead processes: 693
     system statistics:

这里证明使用gdb–>print ksudss(10)对数据库做的是systemstate level 10

验证做gdb的进程

SQL> select * from dual;
D
-
X
SQL> exit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

证明被gdb处理过的进程还是正常(未收到额外破坏),所以我们可以确定在系统hang住，而且新会话不能正常建立连接的时候，我们可以尝试着使用ksudss(10)来对系统做systemstate然后分析