ORA-12514 The TNS listener is currently unable to identify the resolution of the request service in the connection descriptor

Today, using PL/SQL to connect the Oracle database in the virtual machine, it is reported that the "ORA-12514 TNS Listener does not currently recognize the request service in the connection descriptor " error, perhaps you have encountered it for the following reasons:

After the successful installation of Oracle, the database has not been stopped (that is, the database is started), and after the client configuration is successful, there should be no problem.

Sometimes when Oracle is installed in a virtual machine, and after Oracle is installed, no listening configuration is being performed, then the virtual machine restarts, and a ORA-12514 problem occurs.

Here's how to solve the idea:

The client does not hear the instance service name according to the error message

1. Start the database by restarting the service, and again the connection is still unable to connect to the server.

2, since the first method does not solve the problem, then the second method, consider listening Listener.ora

You may not have to specify the service name for the listener in the Listener profile Listener.ora (which is not specified after installing oracle10g). Normally, as long as the database starts, the client connects to the database with no problems, but sometimes a ORA-12514 error occurs when a recurring startup is turned off.

Since no listener is specified in the Listener.ora, we can specify the listener instance name in the Listener.ora file so that the problem should be connected.

The steps are as follows:

In Oracle Server Oracle installation directory (my under C:\oracle, everyone is not the same, according to their own situation to find) Network/admin directory found Listener.ora me as shown

# Listener.ora Network Configuration File:c:\oracle\product\10.2.0\db_1\network\admin\listener.ora
# Generated by Oracle configuration tools.

Sid_list_listener =
(Sid_list =
(Sid_desc =
(Sid_name = Plsextproc)
(Oracle_home = C:\oracle\product\10.2.0\db_1)
(program = Extproc)
)
(Sid_desc =
(Global_dbname = ORCL)
(Oracle_home = C:\oracle\product\10.2.0\db_1)
(Sid_name = ORCL)
)
)

LISTENER =
(Description_list =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC) (KEY = EXTPROC1))
(ADDRESS = (PROTOCOL = TCP) (HOST = 192.168.59.129) (PORT = 1521))
)
)

marked red for the part that I added, ORCL is the instance name of the listener.

Then, the Oracle server restarts, the connection is successful again, this is the configuration of Listener.ora after monitoring, often forget,

Try again, you can see that the client can connect to the Oracle server, and PL/SQL is connected again and there is no problem.

ORA-12514 The TNS listener is currently unable to identify the resolution of the request service in the connection descriptor