如果安装oracle时保持默认安装  那么是 dedicated 模式，官方dedicated架构


那如何转换成共享模式呢！
只要设置shared_servers,max_shared_servers,dispatchers,max_dispatchers参数就可以了
 

C:\Users\Administrator>sqlplus  /nolog

SQL*Plus: Release 10.2.0.4.0 - Production on Wed Jan 8 14:25:03 2014

Copyright (c) 1982, 2007, Oracle.  All Rights Reserved.

SQL> conn / as sysdba
Connected.
SQL> select username,server from v$session where username=user;

USERNAME                       SERVER
------------------------------ ---------
SYS                            DEDICATED

SQL> alter system set shared_servers=3;

System altered.

SQL> alter system set max_shared_servers=3;

System altered.

SQL> alter system set dispatchers='(PROTOCOL=TCP)(dispatchers=3)';

System altered.

SQL> alter system set max_dispatchers=3;

System altered.
以上参数修改后，还要在tnsnames.ora文件中加
 (SERVER=SHARED)

ORCL =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = PC-20121109DQMJ)(PORT = 1521))
    (CONNECT_DATA =
       (SERVER=SHARED)
      (SERVICE_NAME = orcl)
    )
  )

然后 重新登入

SQL> conn sys/smt@orcl as sysdba
Connected.
SQL> select username,server from v$session where username=user;

USERNAME                       SERVER
------------------------------ ---------
SYS                            SHARED

这里必须不能用本地认证方式  如果是本地认证方式的话仍然是专用方式：

SQL> conn /as sysdba
Connected.
SQL> select username,server from v$session where username=user;

USERNAME                       SERVER
------------------------------ ---------
SYS                            DEDICATED