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oracle public redo thread and private redo thread

时间：2014-08-30 19:08:19      阅读：514      评论：0      收藏：0      [点我收藏+]

标签：oracle   redo   thread   log   

复习之前的学习内容，对public redo thread 和 private redo thread 的用处还是比较模糊，网上搜集的资料非常有限，看来有些好东西不跳墙是不行的。

废话少说，知识点记录下来：

在rac环境下，每个实例都有自己的redo log，这套redo log称为redo thread。这套概念同样适用于单实例数据库。

redo thread有两种，private 和 public ，在默认情况下，我们使用的是public thread。但是如果我们在创建redol log时明确指定了thread参数，那么该redo为private redo。

实验如下：


单实例：

SQL> l
  1* select thread#,status,enabled from v$thread
SQL> /

   THREAD# STATUS ENABLED
---------- ------ --------
	 1 OPEN   PUBLIC

SQL> select group#,thread#,status from v$log;

    GROUP#    THREAD# STATUS
---------- ---------- ----------------
	 4	    1 INACTIVE
	 5	    1 CURRENT

SQL> col member for a60
SQL> select group#,member from v$logfile;

    GROUP# MEMBER
---------- ------------------------------------------------------------
	 4 /home/app/oraten/oradata/oraten/redo04.log
	 5 /home/app/oraten/oradata/oraten/redo05.log

SQL> alter database add logfile thread 2 group 6 '/home/app/oraten/oradata/oraten/redo06.log' size 100M;

Database altered.

SQL> alter database add logfile thread 2 group 7 '/home/app/oraten/oradata/oraten/redo07.log' size 100M;

Database altered.

SQL> select thread#,status,enabled from v$thread;

   THREAD# STATUS ENABLED
---------- ------ --------
	 1 OPEN   PUBLIC
	 2 CLOSED DISABLED

SQL> alter database enable thread 2;

Database altered.

SQL> select thread#,status,enabled from v$thread;

   THREAD# STATUS ENABLED
---------- ------ --------
	 1 OPEN   PUBLIC
	 2 CLOSED PRIVATE

SQL> show parameter thread

NAME				     TYPE	 VALUE
------------------------------------ ----------- ------------------------------
parallel_threads_per_cpu	     integer	 2
thread				     integer	 1
SQL> alter system set thread=2 scope=spfile;

System altered.

SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.

Total System Global Area  281018368 bytes
Fixed Size		    2095672 bytes
Variable Size		  222299592 bytes
Database Buffers	   50331648 bytes
Redo Buffers		    6291456 bytes
Database mounted.
Database opened.
SQL> select thread#,status,enabled from v$thread;

   THREAD# STATUS ENABLED
---------- ------ --------
	 1 CLOSED PUBLIC
	 2 OPEN   PRIVATE

SQL> select group#,thread#,status from v$log;

    GROUP#    THREAD# STATUS
---------- ---------- ----------------
	 4	    1 INACTIVE
	 5	    1 CURRENT
	 6	    2 CURRENT
	 7	    2 UNUSED

SQL>

Rac环境下：


 
[oracle@node1 ~]$ crs_stat -t -v
Name           Type           R/RA   F/FT   Target    State     Host        
----------------------------------------------------------------------
ora.easy.db    application    0/0    0/1    ONLINE    ONLINE    node1       
ora....y1.inst application    0/5    0/0    ONLINE    ONLINE    node1       
ora....y2.inst application    0/5    0/0    ONLINE    ONLINE    node2       
ora....SM1.asm application    0/5    0/0    ONLINE    ONLINE    node1       
ora....E1.lsnr application    0/5    0/0    ONLINE    ONLINE    node1       
ora.node1.gsd  application    0/5    0/0    ONLINE    ONLINE    node1       
ora.node1.ons  application    0/3    0/0    ONLINE    ONLINE    node1       
ora.node1.vip  application    0/0    0/0    ONLINE    ONLINE    node1       
ora....SM2.asm application    0/5    0/0    ONLINE    ONLINE    node2       
ora....E2.lsnr application    0/5    0/0    ONLINE    ONLINE    node2       
ora.node2.gsd  application    0/5    0/0    ONLINE    ONLINE    node2       
ora.node2.ons  application    0/3    0/0    ONLINE    ONLINE    node2       
ora.node2.vip  application    0/0    0/0    ONLINE    ONLINE    node2       

[oracle@node1 ~]$ 
[oracle@node1 ~]$ sqlplus / as sysdba

SQL*Plus: Release 10.2.0.5.0 - Production on Sat Aug 30 17:47:08 2014

Copyright (c) 1982, 2010, Oracle.  All Rights Reserved.


Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.5.0 - 64bit Production
With the Partitioning, Real Application Clusters, OLAP, Data Mining
and Real Application Testing options

SQL> desc v$thread
 Name					   Null?    Type
 ----------------------------------------- -------- ----------------------------
 THREAD#					    NUMBER
 STATUS 					    VARCHAR2(6)
 ENABLED					    VARCHAR2(8)
 GROUPS 					    NUMBER
 INSTANCE					    VARCHAR2(80)
 OPEN_TIME					    DATE
 CURRENT_GROUP# 				    NUMBER
 SEQUENCE#					    NUMBER
 CHECKPOINT_CHANGE#				    NUMBER
 CHECKPOINT_TIME				    DATE
 ENABLE_CHANGE# 				    NUMBER
 ENABLE_TIME					    DATE
 DISABLE_CHANGE#				    NUMBER
 DISABLE_TIME					    DATE
 LAST_REDO_SEQUENCE#				    NUMBER
 LAST_REDO_BLOCK				    NUMBER
 LAST_REDO_CHANGE#				    NUMBER
 LAST_REDO_TIME 				    DATE

SQL> select thread#,status,enabled from v$thread;

   THREAD# STATUS ENABLED
---------- ------ --------
	 1 OPEN   PUBLIC
	 2 OPEN   PUBLIC

SQL> show parameter thread

NAME				     TYPE	 VALUE
------------------------------------ ----------- ------------------------------
parallel_threads_per_cpu	     integer	 2
thread				     integer	 1
SQL> exit
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.5.0 - 64bit Production
With the Partitioning, Real Application Clusters, OLAP, Data Mining
and Real Application Testing options
[oracle@node1 ~]$ ssh oracle@node2
Last login: Mon Aug 25 13:09:51 2014 from node3
[oracle@node2 ~]$ sqlplus / as sysdba

SQL*Plus: Release 10.2.0.5.0 - Production on Sat Aug 30 17:48:27 2014

Copyright (c) 1982, 2010, Oracle.  All Rights Reserved.


Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.5.0 - 64bit Production
With the Partitioning, Real Application Clusters, OLAP, Data Mining
and Real Application Testing options

SQL> show parameter thread

NAME				     TYPE	 VALUE
------------------------------------ ----------- ------------------------------
parallel_threads_per_cpu	     integer	 2
thread				     integer	 2

SQL> alter system set thread=1 scope=spfile sid='easy2';

System altered.

SQL> alter system set thread=2 scope=spfile sid='easy1';

System altered.

SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> exit
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.5.0 - 64bit Production
With the Partitioning, Real Application Clusters, OLAP, Data Mining
and Real Application Testing options
[oracle@node2 ~]$ exit
logout

Connection to node2 closed.
[oracle@node1 ~]$ sqlplus / as sysdba

SQL*Plus: Release 10.2.0.5.0 - Production on Sat Aug 30 17:55:54 2014

Copyright (c) 1982, 2010, Oracle.  All Rights Reserved.


Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.5.0 - 64bit Production
With the Partitioning, Real Application Clusters, OLAP, Data Mining
and Real Application Testing options

SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.

Total System Global Area  205520896 bytes
Fixed Size		    2095088 bytes
Variable Size		  121636880 bytes
Database Buffers	   75497472 bytes
Redo Buffers		    6291456 bytes
Database mounted.
Database opened.
SQL> show parameter thread

NAME				     TYPE	 VALUE
------------------------------------ ----------- ------------------------------
parallel_threads_per_cpu	     integer	 2
thread				     integer	 2
SQL> exit
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.5.0 - 64bit Production
With the Partitioning, Real Application Clusters, OLAP, Data Mining
and Real Application Testing options
[oracle@node1 ~]$ ssh oracle@node2
Last login: Sat Aug 30 17:54:14 2014 from node1
[oracle@node2 ~]$ sqlplus / as sysdba

SQL*Plus: Release 10.2.0.5.0 - Production on Sat Aug 30 17:57:00 2014

Copyright (c) 1982, 2010, Oracle.  All Rights Reserved.

Connected to an idle instance.

SQL> startup
ORACLE instance started.

Total System Global Area  205520896 bytes
Fixed Size		    2095088 bytes
Variable Size		  100665360 bytes
Database Buffers	   96468992 bytes
Redo Buffers		    6291456 bytes
Database mounted.
Database opened.
SQL> show parameter thread

NAME				     TYPE	 VALUE
------------------------------------ ----------- ------------------------------
parallel_threads_per_cpu	     integer	 2
thread				     integer	 1
SQL> desc gv$log   
 Name					   Null?    Type
 ----------------------------------------- -------- ----------------------------
 INST_ID					    NUMBER
 GROUP# 					    NUMBER
 THREAD#					    NUMBER
 SEQUENCE#					    NUMBER
 BYTES						    NUMBER
 MEMBERS					    NUMBER
 ARCHIVED					    VARCHAR2(3)
 STATUS 					    VARCHAR2(16)
 FIRST_CHANGE#					    NUMBER
 FIRST_TIME					    DATE

SQL> select inst_id,group#,thread# from gv$log;

   INST_ID     GROUP#	 THREAD#
---------- ---------- ----------
	 1	    1	       1
	 1	    2	       1
	 1	    3	       2
	 1	    4	       2
	 2	    1	       1
	 2	    2	       1
	 2	    3	       2
	 2	    4	       2

8 rows selected.

SQL> show parameter thread

NAME				     TYPE	 VALUE
------------------------------------ ----------- ------------------------------
parallel_threads_per_cpu	     integer	 2
thread				     integer	 1

SQL> select thread#,status,enabled from v$thread
  2  ;

   THREAD# STATUS ENABLED
---------- ------ --------
	 1 OPEN   PUBLIC
	 2 OPEN   PUBLIC

SQL> alter database add logfile thread 3 group 5 '+DG4' size 50M;

Database altered.


SQL> alter database add logfile member '+DG4' to group 5;

Database altered.


SQL> alter database add logfile thread 3 group 6 '+DG4' size 50M;

Database altered.

SQL> alter database add logfile member '+DG4' to group 6;

Database altered.

SQL> alter database enable thread 3;

Database altered.

SQL> select thread#,status,enabled from v$thread;

   THREAD# STATUS ENABLED
---------- ------ --------
	 1 OPEN   PUBLIC
	 2 OPEN   PUBLIC
	 3 CLOSED PRIVATE

结论：如果我们使用add logifle 语句时，指定的thread大于instancde_number,就会产生private thread(个人猜测),只有private thread的作用，目前尚未发现有特别的用处



oracle public redo thread and private redo thread

标签：oracle   redo   thread   log   

原文地址：http://blog.csdn.net/yidian815/article/details/38945377
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