最近在使用以前服务器的listner的时候，出现“不能识别当前的链接”，找了很多资料很少无奈，后来静下来想了一下客户端坚挺不到oracle，说明是服务器dispatcher的问题：
查看了一下dispatcher的参数：
SQL>show parameter dispachers;
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------ dispatchers string max_dispatchers integer没有内容，添加一下服务器的配置：
SQL>alter system set dispatchers='(ADDRESS=(PROTOCOL=TCP)(HOST=NAME)(PORT=port)) scope=spile;
system altered.
可以查看一下我们修改的配置：
SQL> select name,network,paddr,status from v$dispatcher;
NAME
---- NETWORK -------------------------------------------------------------------------------- PADDR STATUS -------- ---------------- D000 (ADDRESS=(PROTOCOL=tcp)(HOST=gyc)(PORT=37090)) 2C21A6EC WAIT另外一个原因是监听不是本地的默认LISTENER监听修改成本地的监听。
SQL>alter system set local_listener='local_listener';
查看一下本地的监听：
SQL> show parameter local_listener;
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------ local_listener string (ADDRESS=(PROTOCOL=TCP)(HOST=g yc)(PORT=1522))
静态监听和动态监听：
[oracle@gyc ~]$ lsnrctl status
LSNRCTL for Linux: Version 10.2.0.1.0 - Production on 04-AUG-2011 22:07:39
Copyright (c) 1991, 2005, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=gyc)(PORT=1521)))
STATUS of the LISTENER ------------------------ Alias LISTENER Version TNSLSNR for Linux: Version 10.2.0.1.0 - Production Start Date 04-AUG-2011 20:48:53 Uptime 0 days 1 hr. 18 min. 46 sec Trace Level off Security ON: Local OS Authentication SNMP OFF Listener Parameter File /opt/oracle/product/10.2.0/db_1/network/admin/listener.ora Listener Log File /opt/oracle/product/10.2.0/db_1/network/log/listener.log Listening Endpoints Summary... (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=gyc)(PORT=1521))) 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 UNKNOWN, has 1 handler(s) for this service... The command completed successfully
静态监听显示的是“uknow“ ，动态的显示的ready如下所示：
[oracle@gyc ~]$ lsnrctl status listener1
LSNRCTL for Linux: Version 10.2.0.1.0 - Production on 04-AUG-2011 22:08:31
Copyright (c) 1991, 2005, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=gyc)(PORT=1522)))
STATUS of the LISTENER ------------------------ Alias listener1 Version TNSLSNR for Linux: Version 10.2.0.1.0 - Production Start Date 04-AUG-2011 20:59:02 Uptime 0 days 1 hr. 9 min. 28 sec Trace Level off Security ON: Local OS Authentication SNMP OFF Listener Parameter File /opt/oracle/product/10.2.0/db_1/network/admin/listener.ora Listener Log File /opt/oracle/product/10.2.0/db_1/network/log/listener1.log Listening Endpoints Summary... (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=gyc)(PORT=1522))) Services Summary... 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... The command completed successfully
静态监听的listener.ora的内容如下：
SID_LIST_LISTENER =
(SID_LIST = (SID_DESC = (SID_NAME = PLSExtProc) (ORACLE_HOME = /opt/oracle/product/10.2.0/db_1) (PROGRAM = extproc) ) (SID_DESC = (GLOBAL_DBNAME = orcl) (ORACLE_HOME = /opt/oracle/product/10.2.0/db_1) (SID_NAME = orcl) ) )LISTENER =
(DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = gyc)(PORT = 1521)) )
动态的如下：
LISTENER1 =
(DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = gyc)(PORT = 1522)) )SID_LIST_LISTENER =
(SID_LIST = (SID_DESC = (SID_NAME = PLSExtProc) (ORACLE_HOME = /opt/oracle/product/10.2.0/db_1) (PROGRAM = extproc) ) (SID_DESC = (GLOBAL_DBNAME = orcl) (ORACLE_HOME = /opt/oracle/product/10.2.0/db_1) (SID_NAME = orcl) ) )
关于service
[oracle@gyc ~]$ lsnrctl service
LSNRCTL for Linux: Version 10.2.0.1.0 - Production on 04-AUG-2011 22:09:44
Copyright (c) 1991, 2005, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=gyc)(PORT=1521)))
Services Summary... Service "PLSExtProc" has 1 instance(s). Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service... Handler(s): "DEDICATED" established:0 refused:0 LOCAL SERVER Service "orcl" has 1 instance(s). Instance "orcl", status UNKNOWN, has 1 handler(s) for this service... Handler(s): "DEDICATED" established:0 refused:0 LOCAL SERVER The command completed successfully
上面显示的是两个静态链接，服务名是orcl,实例名也是orcl， 显示的是静态监听；
"DEDICATED" established:0 refused:0
LOCAL SERVER The command completed successfully表示专有链接：链接为0，拒绝为0
专有链接：
每一个连接到数据库的客户端请求，会和客户端之间建立起连接，这个连接用于专门处理该客户端的所有请求，直到用户主动断开连接或网络出现中断。在连接处于空闲时，后台进程PMON会每隔一段时间，就会用户连接状况，如果连接已断开，PMON会清理现场，释放相关的资源。 专用连接相当于一对一的连接，能够快速的响应用户的请求。当然，在连接的时候，首先要创建PGA（Program global area）。
共享链接：
采用共享连接可以有效的提高服务器资源的利用率，但是对一个分配器，只支持一种，每个分配器有自已的排队队列，在请求的任务完成后，由分配器将操作结果返回给相应的用户进程。但是共享连接的建立， 需要Oracle的监听进程、分配器、共享服务器进程才能共同完成一个连接的创建，所以连接的分配也需要一定的时间和资源。
如何选择这两种连接方式：
在理想的情况下，对于长事务或大事务，使用专用连接，可以有效的提高系统的性能，减少用户等待和事务的排队，提高系统的利用率。对于超短事务和短事务、小事务，使用共享连接方式，可以在资源与效率之间达到一种平稀。比如对于OLTP 系统，使用专用连接，而对于网站等，可以使用共享连接。