disconnect session和kill session的區別 轉

原文連線：http://blog.itpub.net/15480802/viewspace-736634/

防止連線過期，內容複製如下：

最常用的殺死oracle程式的方法是alter system kill session ‘sid,serial#’。

但是今天遇到一些意外，資料庫有個從6月12號執行至今的sql，經客戶確認需要將其幹掉，登陸資料庫執行alter system kill。

於是有了以下情形

SQL> alter system kill session '137,7818';

alter system kill session '137,7818'

*

ERROR at line 1:

ORA-00031: session marked for kill

 

SQL> select status,event from v$session where sid = 137;

STATUS   EVENT

-------- ----------------------------------------------------------------

KILLED   SQL*Net more data from dblink

 

SQL>  select object_id,locked_mode,session_id from v$locked_object;

OBJECT_ID LOCKED_MODE SESSION_ID

---------- ----------- ----------

       165           3        137

    104489           3        137

       212           3        137

 

SQL> select TYPE,LMODE,REQUEST,BLOCK from v$lock where sid=137;

TY      LMODE    REQUEST      BLOCK

-- ---------- ---------- ----------

JQ          6          0          0

JI          6          0          0

TM          3          0          0

TM          3          0          0

TM          3          0          0

TX          6          0          0

 

SQL> select t.status, s.status from v$transaction t, v$session s where s.taddr = t.addr and s.sid=137;

STATUS           STATUS

---------------- --------

ACTIVE           KILLED

 

該session已經被標誌為killed，但是其對應的transaction依舊為active，且對應的lock沒有被釋放；

又因為該instance由其他OS使用者啟動，當前登入的使用者沒有許可權執行kill -9

ora_10@justin_$ ps -ef | grep 15616

ora_xxx 15616     1  0   Jul 06 ?        0:22 ora_j001_GLIMSP

ora_10  20035 17648  0 08:23:18 pts/7    0:00 grep 15616

ora_10@justin_$ kill -9 15616

kill: 15616: permission denied

 

不是太清楚到底發生了什麼事情，但此時可使用disconnect session，請參考以下解釋

The KILL SESSION command doesn’t actually kill the session. It merely asks the session to kill itself. In some situations, like waiting for a reply from a remote database or rolling back transactions, the session will not kill itself immediately and will wait for the current operation to complete. In these cases the session will have a status of “marked for kill”. It will then be killed as soon as possible.

The ALTER SYSTEM DISCONNECT SESSION syntax as an alternative method for killing Oracle sessions. Unlike the KILL SESSION command which asks the session to kill itself, the DISCONNECT SESSION command kills the dedicated server process (or virtual circuit when using Shared Sever), which is equivalent to killing the server process from the operating system. The basic syntax is similar to the KILL SESSION command with the addition of the POST_TRANSACTION clause. The SID and SERIAL# values of the relevant session can be substituted into one of the following statements.

The POST_TRANSACTION clause waits for ongoing transactions to complete before disconnecting the session, while the IMMEDIATE clause disconnects the session and ongoing transactions are recovered immediately.

http://fatihacar.com/blog/show-and-kill-transaction-lock-in-oracle/

SQL> alter system disconnect session '137,7818' immediate;

 

System altered.

 

SQL> select serial#,status,event from v$session where sid=137;

 

   SERIAL# STATUS

---------- --------

EVENT

----------------------------------------------------------------

      7822 ACTIVE

jobq slave wait

 

 

SQL> alter system disconnect session '137,7822' immediate;

 

System altered.

 

SQL> select serial#,status,event from v$session where sid=137;

 

no rows selected

 

SQL> select object_id,locked_mode,session_id from v$locked_object;

 

 OBJECT_ID LOCKED_MODE SESSION_ID

---------- ----------- ----------

       165           3        132

    104489           3        132

       212           3        132

 

SQL> select serial#,event,status,sql_id from v$session where sid=132;

 

   SERIAL# EVENT

---------- ----------------------------------------------------------------

STATUS   SQL_ID

-------- -------------

     24231 jobq slave wait

ACTIVE

 

 

SQL> alter system disconnect session '132,24231' immediate;

 

System altered.

 

SQL> select object_id,locked_mode,session_id from v$locked_object;

 

no rows selected

 

--此時session被徹底清除，對應的lock

也已釋放

--========================================

alter system disconnect session有兩個選項，一個是post_transaction,另外一個是immediate

alter session disconnect session 'sid,serial#' post_transaction;

alter session disconnect session 'sid,serial#' immediate;

post_transaction會等待session做完當前的transaction後再殺死session,而immediate不會等待當前程式完成，類似於alter system kill session。