当数据库出现一些挂起状态时，如果sqlplus仍然可以连接，可能视图查询没有相应，但是可以通过oradebug工具来进行进程及系统状态信息的转储，从而可以进行Hang分析。
DUMP进程状态可以使用：

alter sessions set events 'immediate trace name processstate level ';

或者使用：

oradebug setmypid
oradebug ulimit
oradebug dump processstate

当诊断数据库挂起条件时可以DUMP系统状态：
alter sessions set events 'immediate trace name systemstate level '；
或：
oradebug setmypid
oradebug ulimit
oradebug dump systemstate

如果为了获取全面一点的信息，可以使用Level 10。
SQL>oradebug setmypid
SQL>oradebug unlimit
SQL>oradebug dump systemstate 10
今天一个朋友的请求帮助，获得的系统状态如下： System State 1
~~~~~~~~~~~~~~~~
1:                                     
2:  waiting for 'pmon timer'            wait
3:  waiting for 'rdbms ipc message'     wait
4:  waiting for 'rdbms ipc message'     wait
5:  waiting for 'rdbms ipc message'     wait
6:  waiting for 'rdbms ipc message'     wait
7:  waiting for 'rdbms ipc message'     wait
8:  waiting for 'buffer busy waits' (2,9,11) wait
9:  waiting for 'rdbms ipc message'     wait
10: waiting for 'rdbms ipc message'     wait
11: waiting for 'log file switch (archiving needed)' wait
12: waiting for 'rdbms ipc message'     wait
13:                                    
14:                                    
15: waiting for 'log file switch (archiving needed)' wait
16: waiting for 'library cache lock'   [LOCK: handle=20e750ca8] wait
17: waiting for 'rdbms ipc message'     wait
18: waiting for 'rdbms ipc message'     wait
19: waiting for 'buffer busy waits' (2,59,1b) wait
     Cmd: Select
20: waiting for 'log file switch (archiving needed)' wait
21: waiting for 'Streams AQ: qmn coordinator idle wait' wait
22: waiting for 'SQL*Net message from client' wait
23: waiting for 'SQL*Net message from client' wait
24: waiting for 'library cache lock'   [LOCK: handle=20e750ca8] wait
25: waiting for 'buffer busy waits' (1,2ba2,1) wait
26: last wait for 'SQL*Net message from client'
…………………………………………………………………
243:waiting for 'log file switch (archiving needed)' wait
     Cmd: Select
248:waiting for 'SQL*Net message from client' wait
249:waiting for 'SQL*Net message from client' wait
250:waiting for 'SQL*Net message from client' wait
251:waiting for 'SQL*Net message from client' wait
252:waiting for 'log file switch (archiving needed)' wait
…………………………………………………………………
273:waiting for 'log file switch (archiving needed)' wait
     Cmd: Insert
Blockers
~~~~~~~~
    Above is a list of all the processes. If they are waiting for a resource
    then it will be given in square brackets. Below is a summary of the
    waited upon resources, together with the holder of that resource.
    Notes:
    ~~~~~
     o A process id of '???' implies that the holder was not found in the
       systemstate.
                    Resource Holder State
      LOCK: handle=20e750ca8    15: waiting for 'log file switch (archiving needed)'
Object Names
~~~~~~~~~~~~
LOCK: handle=20e750ca8    TABL:EXFSYS.RLM$EVTCLEANUP   
显然是归档满了，导致了系统挂起。