Oracle体系结构及备份（十六）——bg-ckpt

一  什么是CKPT进程

 

        作用：

                发出信号给DBWn

                更新数据文件头

                更新控制文件

 

        At specific times, all modified databasebuffers in the system global area are written to the datafiles by DBWn. Thisevent is called a checkpoint. The checkpoint process is responsible forsignalling DBWn at checkpoints and updating all the datafiles and control filesof the database to indicate the most recent checkpoint.

 

二  操作示例

[oracle@localhost 桌面]$ ps -ef | grep ora_
oracle    6491     1  0 11:17 ?        00:00:00 ora_pmon_orcl
oracle    6493     1  0 11:17 ?        00:00:00 ora_psp0_orcl
oracle    6495     1  0 11:17 ?        00:00:00 ora_mman_orcl
oracle    6497     1  0 11:17 ?        00:00:00 ora_dbw0_orcl
oracle    6499     1  0 11:17 ?        00:00:00 ora_lgwr_orcl
oracle    6501     1  0 11:17 ?        00:00:00 ora_ckpt_orcl
oracle    6503     1  0 11:17 ?        00:00:00 ora_smon_orcl
oracle    6505     1  0 11:17 ?        00:00:00 ora_reco_orcl
oracle    6507     1  0 11:17 ?        00:00:00 ora_cjq0_orcl
oracle    6509     1  0 11:17 ?        00:00:00 ora_mmon_orcl
oracle    6511     1  0 11:17 ?        00:00:00 ora_mmnl_orcl
oracle    6513     1  0 11:17 ?        00:00:00 ora_d000_orcl
oracle    6515     1  0 11:17 ?        00:00:00 ora_s000_orcl
oracle    6519     1  0 11:17 ?        00:00:00 ora_qmnc_orcl
oracle    6527     1  0 11:18 ?        00:00:00 ora_q000_orcl
oracle    6529     1  0 11:18 ?        00:00:00 ora_q001_orcl
oracle    6538     1  0 11:19 ?        00:00:00 ora_j000_orcl
oracle    6541  2720  0 11:19 pts/0    00:00:00 grep ora_
[oracle@localhost 桌面]$ ps -ef | grep ora_ | grep ckpt
oracle    6501     1  0 11:17 ?        00:00:00 ora_ckpt_orcl
[oracle@localhost 桌面]$ kill -9 6501
[oracle@localhost 桌面]$ ps -ef | grep ora_ | grep ckpt
[oracle@localhost 桌面]$ ps -ef | grep ora_
oracle    6554  2720  0 11:20 pts/0    00:00:00 grep ora_
[oracle@localhost 桌面]$ sqlplus / as sysdba;

SQL*Plus: Release 10.2.0.1.0 - Production on Thu Jun 6 11:20:14 2013

Copyright (c) 1982, 2005, Oracle.  All rights reserved.

Connected to an idle instance.

SQL> startup
ORACLE instance started.

Total System Global Area  838860800 bytes
Fixed Size		    1222192 bytes
Variable Size		  788531664 bytes
Database Buffers	   46137344 bytes
Redo Buffers		    2969600 bytes
Database mounted.
Database opened.
SQL> exit;
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options
[oracle@localhost 桌面]$ ps -ef | grep ora_ | grep ckpt
oracle    6568     1  0 11:20 ?        00:00:00 ora_ckpt_orcl

三  总结

 

        1.CKPT，非常非常重要的后台进程，同样不能kill。触发顺序：CKPT------>DBWR------->LGWR

        2.作用：发出信号给DBWn、更新数据文件头、更新控制文件

        3.Linux中使用ps命令查看CKPT进程。

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  By Larry Wen

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