local_listener与remote_listener详述
2011-03-15 16:11阅读：
remote_listener
用于PMON进程把
本地实例注册到集群中的其它监听上,通过使用这个参数,RAC中各节点的监听可以把连接到本地监听上的连接发送到CPU使用率最低的节点的实例上.从而实现服务器端的负载均衡.
RAC里实现load balance作用
简述一下local_listener与remote_listener这两个参数的含义（针对
rac环境）
在
安装完RAC以后，
oracle会自动修改local_listener和remote_listener这两个参数，同时把两个节点的3要素添加到$ORACLE_HOME/network/admin下的tnsnames.ora文件中：
1.查看listeners_devdb服务名配置
[oracle@rac21admin]$ more tnsnames.ora
LISTENERS_DEVDB
=
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST =
rac1-vip)(PORT = 1521))
(ADDRESS = (PROTOCOL = TCP)(HOST =
rac2-vip)(PORT = 1521))
)
2.show parameter local_listener and
remote_listener
[oracle@rac1 admin]$ sqlplus /nolog
SQL>
connsys/oracle@devdb1 as sysdba
Connected.
SQL> show parameter listener
NAME
TYPE
VALUE
------------------------------------ -----------
------------------------------
local_listener
string (ADDRESS = (PROTOCOL
= TCP)(HOST = 192.168.230.68)(PORT = 1521))
remote_listener
string
LISTENERS_DEVDB
SQL> connsys/oracle@devdb2as sysdba
Connected.
SQL> show parameter listener
NAME
TYPE
VALUE
------------------------------------ -----------
------------------------------
local_listener
string
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.230.69)(PORT =
1521))
remote_listener
string
LISTENERS_DEVDB
3.查看listener状态
节点1
[oracle@rac1 admin]$lsnrctl status
Connecting
to (ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521))
STATUS of the LISTENER
------------------------
Alias
LISTENER_RAC1
Version
TNSLSNR for Linux: Version 10.2.0.4.0 -
Production
Start Date
28-APR-2009 10:36:56
Uptime
0 days 8 hr. 1 min. 20 sec
Trace Level
off
Security
ON: Local OS Authentication
SNMP
OFF
Listener Parameter File
/u01/app/oracle/product/10.2.0/db_1/network/admin/listener.ora
Listener Log File
/u01/app/oracle/product/10.2.0/db_1/network/log/listener_rac1.log
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.230.68)(PORT=1521)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=127.0.0.1)(PORT=1521)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC)))
Services Summary...
Service 'devdb' has 2 instance(s).
Instance 'devdb1', status READY, has 2
handler(s) for this service...
Instance 'devdb2', status READY, has 1 handler(s) for this
service...
The command completed
successfully
[oracle@rac1 admin]$lsnrctl
service
Connecting to
(ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521))
Services Summary...
Service 'devdb' has 2 instance(s).
Instance 'devdb1', status READY, has 2 handler(s) for this
service...
Handler(s):
'DEDICATED' established:1
refused:0 state:ready
LOCAL SERVER
--local_listener参数
'DEDICATED' established:0 refused:0 state:ready
REMOTE SERVER
--remote_listener参数
(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.230.68)(PORT=1521))
Instance 'devdb2', status READY, has 1 handler(s) for this
service...
Handler(s):
'DEDICATED' established:0
refused:0 state:ready
REMOTE SERVER
--remote_listener参数
(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.230.69)(PORT=1521))
The
command completed successfully
节点2
[oracle@rac2 admin]$lsnrctl
status
Connecting to
(ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521))
STATUS of the LISTENER
------------------------
Alias
LISTENER_RAC2
Version
TNSLSNR for Linux: Version 10.2.0.4.0 -
Production
Start Date
28-APR-2009 15:25:45
Uptime
0 days 3 hr. 18 min. 21 sec
Trace Level
off
Security
ON: Local OS Authentication
SNMP
OFF
Listener Parameter File
/u01/app/oracle/product/10.2.0/db_1/network/admin/listener.ora
Listener Log File
/u01/app/oracle/product/10.2.0/db_1/network/log/listener_rac2.log
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.230.69)(PORT=1521)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.230.67)(PORT=1521)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC)))
Services Summary...
Service 'devdb' has 2 instance(s).
Instance 'devdb1', status READY, has
1 handler(s) for this service...
Instance 'devdb2', status READY, has 2 handler(s) for this
service...
The command completed successfully
[oracle@rac2 admin]$lsnrctl
service
Connecting to
(ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521))
Services Summary...
Service 'devdb' has 2 instance(s).
Instance 'devdb1', status READY, has 1 handler(s) for this
service...
Handler(s):
'DEDICATED' established:0
refused:0 state:ready
REMOTE SERVER
--remote_listener参数
(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.230.68)(PORT=1521))
Instance 'devdb2', status READY, has 2 handler(s) for this
service...
Handler(s):
'DEDICATED' established:0
refused:0 state:ready
REMOTE SERVER
--remote_listener参数
(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.230.69)(PORT=1521))
'DEDICATED' established:1
refused:0 state:ready
LOCAL SERVER
--local_listener参数
The command
completed successfully
过程描述：
当客户端发出连接请求给
server端
listener的时候，通过local_listener注册的服务接收这个连接请求，然后由master
instance来决定这个连接请求应该由哪个目标instance发出server
process响应这个连接请求。如果启用负载均衡，那么主节点会选择cpu负载最小的那个instance，此时
如果master分配的目标instance是local
listener machine，那么直接通过local server listener，开启后台的server
process，处理发出conn的客户端，建立连接，处理会话;
如果master分配的目标instance不是local listener
machine，那么会通过remote_listener这个参数，把连接请求转移到remote machine上的listener,
然后由remote service listener发出一个server process返回客户端，建立连接，处理会话.
当conn建立连接以后，listener就没有用了，不会再用到了，如果这个时候，已经连接的那个instance
down了，会重新由新分配的master
instance通过remote_listener切换到可用instance，此时客户不会发现连接中断。conn 和
select操作是不会中断的。
备注：shut down
instance2，重启listener，测试监听服务状态
[oracle@rac2 admin]$ sqlplus /nolog
SQL> connsys/oracle@devdb2as
sysdba
Connected.
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> exit
[oracle@rac2 admin]$
