Required parameter:dispatchers
optional parameters:
shared_servers、max_shared_servers、circuits、shared_server_sessions
这5个参数均是动态参数，可以动态修改。

[@more@]

DISPATCHERS = “(PROTOCOL=TCP)(DISPATCHERS=2)(PROTOCOL=IPC)(DISPATCHERS=1)”
dispatchers的属性值中还可以有如下参数
service：dispatcher注册的net service name，没有给出采用services_name中的；
listener：监听动态注册，非默认端口1521或没有在local_listener中给出时需使用；
sessions：每个dispacther的会话数
connections：每个dispacther连接数

通过查询v$circuit看是否使用到dispacther，也即是否是shared server模式，
另外也可通过lsnrctl services来查看是否shared server模式。
SQL> alter system set circuits=8;

System altered.

SQL> alter system set max_shared_servers=8
2 ;

System altered.

SQL> alter system set shared_servers=8;

System altered.

SQL> alter system set max_dispatchers=8;

System altered.

SQL> alter system set dispatchers='(PROTOCOL=TCP) (SERVICE=racdb1XDB) (PROTOCOL=TCP) (SERVICE=racdb1)';

System altered.

SQL> select count(*) from v$circuit;

COUNT(*)
----------
1

SQL>
SQL> show parameter disp

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
dispatchers string (PROTOCOL=TCP) (SERVICE=racdb1
XDB) (PROTOCOL=TCP) (SERVICE=r
acdb1)
max_dispatchers integer 8
SQL> show parameter shared_serv

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
max_shared_servers integer 8
shared_server_sessions integer
shared_servers integer 8
SQL>

监听的services状态中有如下信息：
LSNRCTL> services
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.2.168)(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 "racdb1" has 2 instance(s).
Instance "racdb1", status UNKNOWN, has 1 handler(s) for this service...
Handler(s):
"DEDICATED" established:0 refused:0
LOCAL SERVER
Instance "racdb1", status READY, has 2 handler(s) for this service...
Handler(s):
"DEDICATED" established:3 refused:0 state:ready
LOCAL SERVER
"D000" established:1 refused:0 current:1 max:1022 state:ready
DISPATCHER
(ADDRESS=(PROTOCOL=tcp)(HOST=rac1.ocm.com)(PORT=33253))
Service "racdb1XDB" has 1 instance(s).
Instance "racdb1", status READY, has 0 handler(s) for this service...
Service "racdb1_XPT" has 1 instance(s).
Instance "racdb1", status READY, has 1 handler(s) for this service...
Handler(s):
"DEDICATED" established:3 refused:0 state:ready
LOCAL SERVER
The command completed successfully
LSNRCTL>