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@devdb2 as 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 succes sfully
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> conn sys/oracle@devdb2 as sysdba Connected. SQL> shutdown immediate; Database closed. Database dismounted. ORACLE instance shut down. SQL> exit [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. 43 min. 44 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 1 instance(s). Instance "devdb1", status READY, has 1 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 1 instance(s). Instance "devdb1", status READY, has 1 handler(s) for this service... Handler(s): "DEDICATED" established:0 refused:0 state:ready REMOTE SERVER (ADDRESS=(PROTOCOL=TCP)(HOST=192.168.230.68)(PORT=1521)) The command completed successfully [oracle@rac2 admin]$ lsnrctl stop Connecting to (ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521)) The command completed successfully [oracle@rac2 admin]$ lsnrctl start Starting /u01/app/oracle/product/10.2.0/db_1/bin/tnslsnr: please wait... TNSLSNR for Linux: Version 10.2.0.4.0 - Production System parameter file is /u01/app/oracle/product/10.2.0/db_1/network/admin/listener.ora Log messages written to /u01/app/oracle/product/10.2.0/db_1/network/log/listener.log Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=rac2.domain.com)(PORT=1521))) Connecting to (ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521)) STATUS of the LISTENER ------------------------ Alias LISTENER Version TNSLSNR for Linux: Version 10.2.0.4.0 - Production Start Date 28-APR-2009 19:11:08 Uptime 0 days 0 hr. 0 min. 0 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.log Listening Endpoints Summary... (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=rac2.domain.com)(PORT=1521))) The listener supports no services The command completed successfully [oracle@rac2 admin]$ lsnrctl status Connecting to (ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521)) STATUS of the LISTENER ------------------------ Alias LISTENER Version TNSLSNR for Linux: Version 10.2.0.4.0 - Production Start Date 28-APR-2009 19:11:08 Uptime 0 days 0 hr. 3 min. 28 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.log Listening Endpoints Summary... (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=rac2.domain.com)(PORT=1521))) Services Summary... Service "devdb" has 1 instance(s). Instance "devdb1", status READY, has 1 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 1 instance(s). Instance "devdb1", status READY, has 1 handler(s) for this service... Handler(s): "DEDICATED" established:0 refused:0 state:ready REMOTE SERVER (ADDRESS=(PROTOCOL=TCP)(HOST=192.168.230.68)(PORT=1521)) The command completed successfully 此时可以看出，即使关闭实例2了，重启listener，但是实例2的service devdb 仍然可用，所以由此可以看出： 当实例1注册监听的时候，即使节点2的instance没有启动，也会通过remote_listener在节点2server上注册相应的listener1.它是在数据库 启动的时候，添加到相应的listener service里的。
