Oracle databases are widely used in the industry; sometimes, you may encounter errors when working with them. One such error is the ORA-01034 Oracle not available error, which indicates that the Oracle database instance is not available. This error can be frustrating, especially when working on a critical project. In this article, we will discuss what this error is, what causes this error, and how to resolve it.

What is ORA-01034 Error?

ORA-01034 is an error code indicating that the Oracle database instance is unavailable. This error usually occurs when the Oracle database service is not running or is not accessible. When you try to connect to the database, you will get the following error message:

ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist

This error can occur on any operating system, including Windows, Linux, and Unix.

Causes of ORA-01034 Error

There can be several causes of the ORA-01034 error. Some of the most common causes are:

1. Oracle Service Not Running

If the Oracle service is not running, you cannot connect to the database instance. The Oracle service can stop due to several reasons, including hardware failure, power outage, or software issues.

2. Incorrect Oracle SID

The Oracle SID is a unique identifier for the database instance. If the Oracle SID is incorrect, you cannot connect to the database instance. This error can occur when you try to connect to a different database instance or when the Oracle SID is misspelled.

3. Invalid Login Credentials

If you use incorrect login credentials, you cannot connect to the database instance. This error can occur when you forget your password or when your account is locked.

4. Database Corruption

Database corruption can also cause the ORA-01034 error. If the database files are corrupted, you will not be able to connect to the database instance. This error can occur due to hardware failure, software issues, or power outages.

How to Resolve ORA-01034 Error

Now that we know the causes of the ORA-01034 error, let’s list the possible ways to resolve it. Here are some steps that you can follow:

• Check Oracle Service
• Verify Oracle SID
• Verify Login Credentials
• Check Database Corruption

Check the Oracle Service

The first step is to check if the Oracle service is running. You can do this by opening the Services app in Windows and checking if the Oracle service is running. If the service is not running, start it and try to connect to the database again.

Verify the Oracle SID

Make sure that you are using the correct Oracle SID. You can check the Oracle SID by running the following command in the command prompt:

echo %ORACLE_SID%

If the Oracle SID is incorrect, set it to the correct value by running the following command:

set ORACLE_SID=sid

Replace “sid” with the correct Oracle SID.

Verify the Login Credentials

Make sure that you are using the correct login credentials. If you forget your password, you can reset it by running the following command:

alter user username identified by new_password;

Replace “username” with your username and “new_password” with your new password.

Check for Database Corruption

If none of the above steps work, check for database corruption. You can do this by running the following command in the command prompt:

sqlplus / as sysdba

If you get the following error message, the database files may be corrupted:

ORA-01157: cannot identify/lock

If you get the above error message, the database files may be corrupted. In this case, you need to restore the database from a backup or perform recovery operations.

To perform recovery operations, you can follow these steps:

1. Open the command prompt and connect to the database using the following command:

sqlplus / as sysdba

2. Check the status of the database using the following command:

startup mount;

3. Recover the database using the following command:

recover database;

4. Open the database using the following command:

alter database open;

Once the database is open, try to connect to it and check if the ORA-01034 error is resolved.

Conclusion

The ORA-01034 error is a common error that occurs when the Oracle database instance is not available. This error can occur due to various reasons, including the Oracle service not running, incorrect Oracle SID, invalid login credentials, and database corruption. To resolve this error, you can follow the steps mentioned above, which include checking the Oracle service, verifying the Oracle SID and login credentials, and checking for database corruption. By following these steps, you can quickly resolve the ORA-01034 error and continue working on your projects.

FAQs

What is the Oracle SID?

Oracle SID is a unique identifier for the database instance.

Why am I getting the ORA-01034 error?

You may be getting the ORA-01034 error due to various reasons, including the Oracle service not running, incorrect Oracle SID, invalid login credentials, and database corruption.

How can I check if the Oracle service is running?

You can check if the Oracle service is running by opening the Services app in Windows and checking if the Oracle service is running.

Can I reset my password if I forget it?

Yes, you can reset your password by running the following command: alter user username identified by new_password;

What should I do if the database files are corrupted?

If the database files are corrupted, you must restore the database from a backup or perform recovery operations.