这里有很多答案，但这里有一个工作示例的代码，你可以立即复制、粘贴和测试:

对我来说，在指定正确的SERVICE_NAME后，错误12514得到了解决。 您可以在服务器上的文件tnsnames中找到它。ora自带3个预定义的服务名称(其中一个是“XE”)。

I installed the Oracle Express database OracleXE112 which already comes with some preinstalled demo tables. When you start the installer you are asked for a password. I entered "xxx" as password. (not used in production) My server runs on the machine 192.168.1.158 On the server you must explicitely allow access for the process TNSLSNR.exe in the Windows Firewall. This process listens on port 1521. OPTION A: For C# (.NET2 or .NET4) you can download ODAC11, from which you have to add Oracle.DataAccess.dll to your project. Additionally this DLL depends on: OraOps11w.dll, oci.dll, oraociei11.dll (130MB!), msvcr80.dll. These DLLs must be in the same directory as the EXE or you must specify the DLL path in: HKEY_LOCAL_MACHINE\SOFTWARE\Oracle\ODP.NET\4.112.4.0\DllPath. On 64 bit machines write additionally to HKLM\SOFTWARE\Wow6432Node\Oracle\... OPTION B: If you have downloaded ODAC12 you need Oracle.DataAccess.dll, OraOps12w.dll, oci.dll, oraociei12.dll (160MB!), oraons.dll, msvcr100.dll. The Registry path is HKEY_LOCAL_MACHINE\SOFTWARE\Oracle\ODP.NET\4.121.2.0\DllPath OPTION C: If you don't want huge DLL's of more than 100 MB you should download ODP.NET_Managed12.x.x.x.xxxxx.zip in which you find Oracle.ManagedDataAccess.dll which is only 4 MB and is a pure managed DLL which works in 32 bit and 64 bit processes as well and depends on no other DLL and does not require any registry entries. The following C# code works for me without any configuration on the server side (just the default installation):

using Oracle.DataAccess.Client;
or
using Oracle.ManagedDataAccess.Client;

....

string oradb = "Data Source=(DESCRIPTION="
    + "(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.1.158)(PORT=1521)))"
    + "(CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=XE)));"
    + "User Id=SYSTEM;Password=xxx;";

using (OracleConnection conn = new OracleConnection(oradb)) 
{
    conn.Open();
    using (OracleCommand cmd = new OracleCommand())
    {
        cmd.Connection  = conn;
        cmd.CommandText = "select TABLESPACE_NAME from DBA_DATA_FILES";

        using (OracleDataReader dr = cmd.ExecuteReader())
        {
            while (dr.Read())
            {
                listBox.Items.Add(dr["TABLESPACE_NAME"]);
            }
        }
    }
}

如果SERVICE_NAME=XE错误，则会得到错误12514。SERVICE_NAME是可选的。你也可以把它放在一边。

我有这个问题，修复是确保在tnsnames。ora SERVICE_NAME是数据库中有效的服务名称。要找出有效的服务名称，您可以在oracle中使用以下查询:

select value from v$parameter where name='service_names'

有一次我更新了tnsnames。奥拉:

TEST =
   (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = *<validhost>*)(PORT = *<validport>*))
    )
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = *<servicenamefromDB>*)
    )
)

然后我就跑:

sqlplus user@TEST

成功! 监听器基本上是在告诉你，不管你使用的是什么service_name，根据DB，都不是一个有效的服务。

(*我从Win7客户端工作站运行sqlplus到远程DB，责怪dba;) *)

在我的情况下，错误是由于监听器没有注册db的服务。我通过注册服务解决了这个问题。例子:

我在tnsnames.ora中的描述符:

LOCALDB =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = LOCALDB)
    )
  )

因此，我继续在侦听器中注册服务。奥拉手动:

SID_LIST_LISTENER =
    (SID_DESC =
      (GLOBAL_DBNAME = LOCALDB)
      (ORACLE_HOME = C:\Oracle\product\11.2.0\dbhome_1)
      (SID_NAME = LOCALDB)
    )

最后，通过命令重新启动监听器:

> lsnrctl stop
> lsnrctl start

完成了!

重启虚拟机对我有用

我知道这是一个老问题，但仍然没有答案。我花了一天的时间研究，但我找到了最简单的解决方案，至少在我的情况下(Windows 2008 R2上的Oracle 11.2)，我想分享。

如果直接查看该错误，则表明侦听器不识别服务名称。但是它把服务名保存在哪里呢?在% ORACLE_HOME % \ \ ADMIN \ listener.ora网络

“SID_LIST”就是一个sid和服务名的列表，它们以一种可以复制或查找的格式配对。

我添加了问题服务名称，然后在Windows“服务”控制面板中，我对Oracle侦听器服务进行了“重新启动”。现在一切都好了。

例如，你的听众。Ora文件最初可能是这样的:

# listener.ora Network Configuration File: C:\app\oracle_user\product\12.1.0\dbhome_1\network\admin\listener.ora
# Generated by Oracle configuration tools.

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (SID_NAME = CLRExtProc)
      (ORACLE_HOME = C:\app\oracle_user\product\12.1.0\dbhome_1)
      (PROGRAM = extproc)
      (ENVS = "EXTPROC_DLLS=ONLY:C:\app\oracle_user\product\12.1.0\dbhome_1\bin\oraclr12.dll")
    )
  )

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
    )
  )

．.． 为了让它识别orcl的服务名称，你可以将它更改为:

# listener.ora Network Configuration File: C:\app\oracle_user\product\12.1.0\dbhome_1\network\admin\listener.ora
# Generated by Oracle configuration tools.

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (SID_NAME = CLRExtProc)
      (ORACLE_HOME = C:\app\oracle_user\product\12.1.0\dbhome_1)
      (PROGRAM = extproc)
      (ENVS = "EXTPROC_DLLS=ONLY:C:\app\oracle_user\product\12.1.0\dbhome_1\bin\oraclr12.dll")
    )
    (SID_DESC = 
        (GLOBAL_DBNAME = orcl)
        (ORACLE_HOME = C:\app\oracle_user\product\12.1.0\dbhome_1)
        (SID_NAME = orcl)
    )
  )

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
    )
  )

对于Dbeaver用户:尝试在连接设置中选择“SID”而不是“服务名称”。