A brief analysis of solutions to Oracle connection errors

When using Oracle database, we often encounter connection errors. This situation will not only affect our work efficiency, but also cause us to waste a lot of time looking for the problem. This article will introduce several common Oracle connection errors and provide corresponding solutions.

1. ORA-12154: TNS: cannot resolve the specified connection identifier

ORA-12154 error is usually caused by the inability to resolve the connection identifier. This error may be caused by the following reasons:

• The specified tnsnames.ora file cannot be found;
• The connection identifier configured in the tnsnames.ora file is incorrect;
• The service name used in the connection does not exist.

Solution:

• Confirm whether the tnsnames.ora file exists and is in the correct location. You can find the file by running the following command: $ find / -name tnsnames.ora;
• Verify that the connection identifier configured in the tnsnames.ora file matches the information of the database instance;
• Confirm whether the service name or SID used is correct.

2. ORA-12514: TNS: The listener does not currently recognize the service requested by the connection descriptor

ORA-12514 error is usually caused by the connection's service name Or the SID does not match the listener configuration. This error may be caused by the following reasons:

• The specified service name or SID is wrong;
• The required service name or SID is not configured in the listener.

Solution:

• Confirm whether the service name or SID used is correct;
• Confirm whether the connection to the required service has been configured in the listener Descriptor;
• Manually restart the listener.

3. ORA-12541: TNS: No listener

ORA-12541 error is usually caused by an inability to connect to the Oracle listener. This error may be caused by the following reasons:

• Oracle listener is not started;
• Network connection problem;
• Incorrect configuration.

Solution:

• Confirm that the Oracle listener has been started and the listening configuration is correct;
• Confirm that the network connection is normal;
• Check whether the configuration files such as tnsnames.ora and listener.ora are correct.

4. ORA-12505: TNS: The listener does not currently support the service request

ORA-12505 errors are usually caused by connecting to the wrong database instance . This error may be caused by the following reasons:

• The service name or SID is incorrect;
• The database instance is not started.

Solution:

• Confirm whether the service name or SID used is correct;
• Confirm whether the database instance has been started.

5. ORA-01017: Invalid account/password, login refused

ORA-01017 error is usually caused by mismatch of account and password. This error may be caused by the following reasons:

• The account or password is entered incorrectly;
• the account has been locked;
• the password has expired.

Solution:

• Confirm whether the account password is correct;
• Check whether the account has been locked;
• Check the account password Has it expired?

Summary:

The above are common connection errors and their solutions when using Oracle database. When encountering a connection error, we need to carefully check every possible cause and troubleshoot step by step. At the same time, you can also view the database log to obtain more detailed error information to help us find the problem faster.

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