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listener之一二

一、注册

    注册就是将数据库作为一个服务注册到监听程序。客户端不需要知道数据库名和实例名,只需要

知道该数据库对外提供的服务名就可以申请连接到数据库。这个服务名可以与实例名一致,也可以不

一致,且可以注册多个服务。

    注册可以分为静态注册与动态注册,下面分别介绍静态注册和动态注册。

二、静态注册

    静态注册就是预先配置好listener.ora文件,配置信息如下:

#listener.ora

SID_LIST_LISTENER =

  (SID_LIST =

    (SID_DESC =

      (SID_NAME = PLSExtProc)

      (ORACLE_HOME = /u01/app/oracle/product/10.2/db_1)

      (PROGRAM = extproc)

    )

    (SID_DESC =

      (SID_NAME = orcl)##数据库的实例名

      (ORACLE_HOME = /u01/app/oracle/product/10.2/db_1)##监听程序所在路径

      (GLOBAL_DBNAME = test01)##数据库对外提供的服务名

    )

  )

LISTENER =

  (DESCRIPTION_LIST =

    (DESCRIPTION =

      (ADDRESS = (PROTOCOL = TCP)(HOST = db01)(PORT = 1521))

      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC0))

    )

  )

当用户通过客户端申请连接数据库时,首先通过监听程序读取listener.ora中的配置信息(无论数据库

是否启动,用户的连接请求都会通过监听程序的检查,因为静态监听是无法识别数据库的启动状态的

,只有用户试图连接数据库时,数据库才会返回相关信息。)

下面我们来看下数据库处于打开和关闭状态时,服务test01的实例状态:

1、打开状态

[[email protected] admin]$ lsnrctl status

LSNRCTL for Linux: Version 10.2.0.1.0 - Production on 16-OCT-2013 06:58:27

Copyright (c) 1991, 2005, Oracle.  All rights reserved.

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=db01)(PORT=1521)))

STATUS of the LISTENER

------------------------

Alias                     LISTENER

Version                   TNSLSNR for Linux: Version 10.2.0.1.0 - Production

Start Date                16-OCT-2013 06:39:09

Uptime                    0 days 0 hr. 19 min. 18 sec

Trace Level               off

Security                  ON: Local OS Authentication

SNMP                      OFF

Listener Parameter File   /u01/app/oracle/product/10.2/db_1/network/admin/listener.ora

Listener Log File         /u01/app/oracle/product/10.2/db_1/network/log/listener.log

Listening Endpoints Summary...

  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=db01)(PORT=1521)))

  (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC0)))

Services Summary...

Service "PLSExtProc" has 1 instance(s).

  Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service...

Service "orcl" has 1 instance(s).

  Instance "orcl", status READY, has 1 handler(s) for this service...

Service "orclXDB" has 1 instance(s).

  Instance "orcl", status READY, has 1 handler(s) for this service...

Service "orcl_XPT" has 1 instance(s).

  Instance "orcl", status READY, has 1 handler(s) for this service...

Service "test01" has 1 instance(s).

  Instance "orcl", status UNKNOWN, has 1 handler(s) for this service...   

=>实例orcl的状态为unknown

The command completed successfully

此时当用户通过客户端连接数据库时:

SQL> conn system/[email protected]

已连接。

2、关闭状态:

[[email protected] admin]$ lsnrctl status

LSNRCTL for Linux: Version 10.2.0.1.0 - Production on 16-OCT-2013 06:54:44

Copyright (c) 1991, 2005, Oracle.  All rights reserved.

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=db01)(PORT=1521)))

STATUS of the LISTENER

------------------------

Alias                     LISTENER

Version                   TNSLSNR for Linux: Version 10.2.0.1.0 - Production

Start Date                16-OCT-2013 06:39:09

Uptime                    0 days 0 hr. 15 min. 35 sec

Trace Level               off

Security                  ON: Local OS Authentication

SNMP                      OFF

Listener Parameter File   /u01/app/oracle/product/10.2/db_1/network/admin/listener.ora

Listener Log File         /u01/app/oracle/product/10.2/db_1/network/log/listener.log

Listening Endpoints Summary...

  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=db01)(PORT=1521)))

  (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC0)))

Services Summary...

Service "PLSExtProc" has 1 instance(s).

  Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service...

Service "test01" has 1 instance(s).

  Instance "orcl", status UNKNOWN, has 1 handler(s) for this service...   

=>实例orcl的状态为unknown

The command completed successfully

此时当用户通过客户端连接数据库时:

SQL> conn system/[email protected]

ERROR:

ORA-01034: ORACLE not available

ORA-27101: shared memory realm does not exist

Linux Error: 2: No such file or directory

由此可知,用户的连接请求通过了监听的检查,但数据库没有打开,于是就返回了ora-01034的错误。

通过上面的实验,验证了当监听静态注册时,服务的实例状态均为unknown,监听程序无法知道数据库

是否处于打开状态。

三、动态注册

    动态注册就是不需预先配置listener.ora文件,而是instance在启动的时候PMON进程根据

init.ora中的instance_name、service_names两个参数将实例和服务动态的注册到listener中。

    注册到监听器中的实例名从init.ora文件中的instance_name参数取得。如果该参数没有设定值,

那么它将取init.ora文件中的db_name值。

    注册到监听器中的服务名从init.ora文件中的参数service_names(该参数可以设置多个值,且值

以逗号分隔)和db_domain取得。如果service_names参数没有设定值,数据库将取init.ora文件中的

db_name值。

    采取动态注册时,listener.ora配置如下:

#listener.ora

SID_LIST_LISTENER =

  (SID_LIST =

    (SID_DESC =

      (SID_NAME = PLSExtProc)

      (ORACLE_HOME = /u01/app/oracle/product/10.2/db_1)

      (PROGRAM = extproc)

    )

  )

LISTENER =

  (DESCRIPTION_LIST =

    (DESCRIPTION =

      (ADDRESS = (PROTOCOL = TCP)(HOST = db01)(PORT = 1521))

      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC0))

    )

  )

    动态注册默认只注册到默认的监听器上(名称是LISTENER、端口是1521、协议是TCP),如果需要向

非默认监听注册,则只需要配置local_listener参数。

四、如何区分静态注册与动态注册

方法一:通过lsnrctl status监测

静态注册的监听实例状态为unknown,动态注册的监听实例状态为ready

方式二:查看listener.ora文件

listener.ora文件中添加了如下信息的为静态注册,没有添加为动态注册

(SID_DESC =

  (SID_NAME = orcl)##数据库的实例名

  (ORACLE_HOME = /u01/app/oracle/product/10.2/db_1)##监听程序所在路径

  (GLOBAL_DBNAME = test01)##数据库对外提供的服务名

)

注:1、由于动态注册监听是通过pmon进程来动态添加的,因此一旦数据库关闭,那么动态注册的服务便立即从监听程序中消除。

2、如果想远程启动数据库,需要通过静态注册。