ORACLE快速完全Kill掉的會話

時間 2019-11-19

原文原文鏈接

在ORACLE數據庫當中，有時候會使用ALTER SYSTEM KILL SESSION 'sid,serial#'殺掉一個會話進程，可是使用這個SQL語句殺掉會話後，數據庫並不會當即釋放掉相關的資源，有時候你會發現鎖定的資源很長時間也不會釋放，即便會話狀態爲「KILLED」，依然會阻塞其它會話。 php

下面根據Eygel的"Oracle中Kill session的研究"，構造一個案例看看kill session到底作了什麼。以下所示 html

會話1：數據庫

 
  SQL> conn etl/etl 
   
  Connected. 
   
  SQL>  update test set status='invalid'; 
   
  55944 rows updated. 
   
  SQL> update test2 set dropped='Y'; 
   
  3090 rows updated.

會話2：服務器

 
  SQL> show user 
   
  USER is "SYS" 
   
  SQL> update etl.test2 set dropped='Y'; 
   
  3090 rows updated.

會話3session

 
  SQL> select saddr,sid,serial#,paddr,username,status from v$session where username =upper('etl') or username =upper('sys'); 
   
  SADDR                   SID    SERIAL# PADDR            USERNAME                       STATUS 
   
  ---------------- ---------- ---------- ---------------- ------------------------------ -------- 
   
  000000025C233B00         27      33353 000000025F1D1FC8 ETL                            INACTIVE 
   
  000000025C23A608         37      11448 000000025F1D27B0 SYS                            ACTIVE 
   
  000000025C24BC50         63      54311 000000025F1D5F08 SYS                            ACTIVE 
   
  SQL> alter system kill session '27,33353'; 
   
  System altered. 
   
  SQL> select saddr,sid,serial#,paddr,username,status from v$session where username =upper('etl') or username =upper('sys'); 
   
  SADDR                   SID    SERIAL# PADDR            USERNAME                       STATUS 
   
  ---------------- ---------- ---------- ---------------- ------------------------------ -------- 
   
  000000025C233B00         27      33353 000000025C21A0B0 ETL                            KILLED 
   
  000000025C23A608         37      11448 000000025F1D27B0 SYS                            ACTIVE 
   
  000000025C24BC50         63      54311 000000025F1D5F08 SYS                            INACTIVE

以下所示，我殺掉了其中兩個會話後，這兩個會話的地址都變爲000000025C21A0B0了（請見PADDR列）。當在Oracle中kill session之後, Oracle只是簡單的把相關session的paddr 指向同一個虛擬地址.此時v$process和v$session失去關聯,進程就此中斷。而後Oracle就等待PMON去清除這些Session.因此一般等待一個被標記爲Killed的Session退出須要花費很長的時間. 若是此時被Kill的process，從新嘗試執行任務，那麼立刻會收到進程中斷的提示，process退出，此時Oracle會當即啓動PMON 來清除該session.這被做爲一次異常中斷處理. oracle

 
  SQL> alter system kill session '63,54311'; 
   
  System altered. 
   
  SQL> select saddr,sid,serial#,paddr,username,status  
   
  from v$session where username =upper('etl') or username =upper('sys'); 
   
  SADDR                   SID    SERIAL# PADDR            USERNAME                       STATUS 
   
  ---------------- ---------- ---------- ---------------- ------------------------------ -------- 
   
  000000025C233B00         27      33353 000000025C21A0B0 ETL                            KILLED 
   
  000000025C23A608         37      11448 000000025F1D27B0 SYS                            ACTIVE 
   
  000000025C24BC50         63      54311 000000025C21A0B0 SYS                            KILLED

咱們根據下面SQL找到進程的地址，而後在v$process裏面找到對應的spid,而後從操做系統中殺掉該進程。app

 
  SQL> select p.addr from v$process p where pid <> 1 
   
    2  minus 
   
    3  select s.paddr from v$session s; 
   
  ADDR 
   
  ---------------- 
   
  000000025F1D1FC8 
   
  000000025F1D5F08 
   
  SQL> select saddr,sid,serial#,paddr,username,status from v$session  
   
      where username =upper('etl') or username =upper('sys'); 
   
  SADDR                   SID    SERIAL# PADDR            USERNAME                       STATUS 
   
  ---------------- ---------- ---------- ---------------- ------------------------------ -------- 
   
  000000025C233B00         27      33353 000000025C21A0B0 ETL                            KILLED 
   
  000000025C23A608         37      11448 000000025F1D27B0 SYS                            ACTIVE 
   
  000000025C24BC50         63      54311 000000025C21A0B0 SYS                            KILLED 
   
  SQL>  select addr, pid, spid, username from v$process where addr in ('000000025F1D1FC8','000000025F1D5F08'); 
   
  ADDR                    PID SPID         USERNAME 
   
  ---------------- ---------- ------------ --------------- 
   
  000000025F1D1FC8         22 12959        oracle 
   
  000000025F1D5F08         38 12971        oracle 
   
  SQL> ! kill -9 12959 
   
  SQL> ! kill -9 12971 
   
  SQL> select saddr,sid,serial#,paddr,username,status  
   
      from v$session where username =upper('etl') or username =upper('sys'); 
   
  SADDR                   SID    SERIAL# PADDR            USERNAME                       STATUS 
   
  ---------------- ---------- ---------- ---------------- ------------------------------ -------- 
   
  000000025C23A608         37      11448 000000025F1D27B0 SYS                            ACTIVE

在ORACLE數據庫殺掉會話進程有三種方式： less

1： ALTER SYSTEM KILL SESSION ide

關於KILL SESSION Clause ，以下官方文檔描述所示，alter system kill session實際上不是真正的殺死會話，它只是將會話標記爲終止。等待PMON進程來清除會話。this

 
  The KILL SESSION clause lets you mark a session as terminated, roll back ongoing transactions, release all session locks, and partially recover session resources. To use this clause, your instance must have the database open. Your session and the session to be terminated must be on the same instance unless you specify integer3.You must identify the session with the following values from the V$SESSION view: 
   
  For integer1, specify the value of the SID column. 
   
  For integer2, specify the value of the SERIAL# column. 
   
  For the optional integer3, specify the ID of the instance where the target session to be killed exists. You can find the instance ID by querying the GV$ tables. 
   
  If the session is performing some activity that must be completed, such as waiting for a reply from a remote database or rolling back a transaction, then Oracle Database waits for this activity to complete, marks the session as terminated, and then returns control to you. If the waiting lasts a minute, then Oracle Database marks the session to be terminated and returns control to you with a message that the session is marked to be terminated. The PMON background process then marks the session as terminated when the activity is complete. 
   
  Whether or not the session has an ongoing transaction, Oracle Database does not recover the entire session state until the session user issues a request to the session and receives a message that the session has been terminated.

可使用ALTER SYSTEM KILL SESSION 'sid,serial#' IMMEDIATE 來快速回滾事物、釋放會話的相關鎖、當即返回當前會話的控制權。

Specify IMMEDIATE to instruct Oracle Database to roll back ongoing transactions, release all session locks, recover the entire session state, and return control to you immediately.

2： ALTER SYSTEM DISCONNECT SESSION

ALTER SYSTEM DISCONNECT SESSION 殺掉專用服務器(DEDICATED SERVER)或共享服務器的鏈接會話，它等價於從操做系統殺掉進程。它有兩個選項POST_TRANSACTION和IMMEDIATE，其中POST_TRANSACTION表示等待事務完成後斷開會話，IMMEDIATE表示中斷會話，當即回滾事務。

SQL> ALTER SYSTEM DISCONNECT SESSION 'sid,serial#' POST_TRANSACTION;

SQL> ALTER SYSTEM DISCONNECT SESSION 'sid,serial#' IMMEDIATE;

3： KILL -9 SPID （Linux）或 orakill ORACLE_SID spid　（Windows）

可使用下面SQL語句找到對應的操做系統進程SPID，而後殺掉。固然殺掉操做系統進程是一件危險的事情，尤爲不要誤殺。因此在執行前，必定要謹慎確認。

 
  SET LINESIZE 100 
   
  COLUMN spid FORMAT A10 
   
  COLUMN username FORMAT A10 
   
  COLUMN program FORMAT A45 
   
  SELECT s.inst_id, 
   
         s.sid, 
   
         s.serial#, 
   
         p.spid, 
   
         s.username, 
   
         s.program 
   
  FROM   gv$session s 
   
         JOIN gv$process p ON p.addr = s.paddr AND p.inst_id = s.inst_id 
   
  WHERE  s.type != 'BACKGROUND';