ORA-12520: TNS: 监听程序无法找到需要的服务器类型的可用句柄。

解决方法
在oracle安装目录下搜索tnsnames.ora（如：G:\oracle\product\10.2.0\db_2\NETWORK\ADMIN）
将其中的共享模式：SHARED

GS =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = GCOQ3XIPLGQ4Y22)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SERVER = SHARED)
      (SERVICE_NAME = gs)
    )
  )

修改为专有模式：DEDICATED

GS =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = GCOQ3XIPLGQ4Y22)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = gs)
    )
  )