FAQs about Oracle client server connection

To eliminate the connection problem between the client and the server, first check whether the client configuration is correct (the client configuration must be consistent with the database server listening configuration), and then solve the problem according to the error prompt. The following lists several common connection problems:
1. ORA-12541: TNS: No listener
Obviously, the server listener is not started, and check whether the client IP address or port is entered correctly. Start the listener (it may need to be started under the Oracle user ):
$ Lsnrctl start
Or
C: \ lsnrctl start
2. ORA-12500: TNS: The Listener cannot start the dedicated server process
For Windows, the Oracle instance service is not started. Start the instance service:
C: \ oradim-startup-sid myoracle
3. ORA-12535: TNS: Operation timeout
There are many reasons for this problem, but it is mainly related to the network. To solve this problem, first check whether the network between the client and the server is smooth. If the network is connected, check whether the firewalls at both ends have blocked the connection.
4. ORA-12154: TNS: unable to process service name
Check whether the entered service name is consistent with the configured service name. In addition, pay attention to the generated local service name file (for example, D: \ oracle \ ora92 \ network \ admin \ tnsnames in Windows. ora, $ ORACLE_HOME/network/admin/tnsnames in Linux/Unix. the name of the first line of each service in ora cannot contain spaces.
5. ORA-12514: TNS: the listener process cannot parse the SERVICE_NAME given in the connection Descriptor
Open Net Manager, select the service name, and check whether the service name entered in the service ID column is correct. The service name must be consistent with the global database name configured by the server listener.
6. In Windows, when the listening service is started, the system prompts that the path cannot be found.
You can run the command or start the listener in the service window. The system prompts that the path cannot be found, or the listening service has an exception. Open the registry, enter the HKEY_LOCAL_MACHINE/SYSTEM/Current ControlSet/Services/OracleOraHome92TNSListener item, and check whether the ImagePath string item exists. If not, set the value to D: \ oracle \ ora92 \ BIN \ TNSLSNR, change the installation path values accordingly. This method is also applicable to Oracle instance Services. Same as above, find items like HKEY_LOCAL_MACHINE/SYSTEM/Current ControlSet/Services/Oracle ServiceMYORACLE to check whether the ImagePath string item exists. If not, create a new one, set the value to d: \ oracle \ ora92 \ binORACLE. exe myoracle.
The above are some common problems for Oracle clients to connect to the server. Of course, it cannot cover all connection exceptions. The key to solving the problem lies in the methods and ideas, rather than having fixed answers to each question.
 
TNS-01155: Incorrectly specified SID_LIST_LISTENER parameter in LISTENER. ORA
TNS-01155: Incorrectly specified SID_LIST_LISTENER parameter in LISTENER. ORA this error occurs because we changed the listener. ora file: So lsnrctl cannot start oracle port 1521. The specific solution is as follows:

Modify $ ORACLE_HOME/network/admin/listener. ora (changed below ). (This problem still cannot be solved after modification according to the online modification method. Finally, you can only refer to the online modification method and $ ORACLE_HOME/network/admin/samples/listener. this problem can be solved only after the syntax rules of the ora file are modified)
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(GLOBAL_DBNAME = orcl)
# (SID_NAME = PLSExtProc)
(ORACLE_HOME =/usr/oracle_db/product/10.2.0 /)
(SID_NAME = orcl)
# (PROGRAM = extproc)
)
)
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC) (KEY = EXTPROC1 ))
(ADDRESS = (PROTOCOL = TCP) (HOST = localhost. localdomain) (PORT = 1521 ))
)
)