Analysis of situations where oracle cannot start

Oracle database is a very popular relational database management system and is widely used. However, sometimes there will be problems starting the Oracle database. This article will analyze the situation of Oracle startup failure and provide corresponding solutions.

1. Check whether the Oracle instance has been started

In the operation of the Oracle database, there may be multiple instances. In order to ensure the normal operation of the system, each instance should be in normal state Operating status. However, we won't be aware of any running instances until we start them. If the instance is already started, startup failure may occur.

At this time, we can run the ps -ef|grep ora_pmon command, which will display the database names of all running Oracle instances. If the results displayed match the instance name you want to start, then the instance already exists and you need to shut it down before trying to restart it.

2. Check the Oracle listener

The Oracle listener is also a very important component because it is responsible for handling the connection request between the client application and the Oracle database. If the Oracle listener cannot run properly, Oracle startup may fail.

We can check the status of the listener by running the lsnrctl status command. If the listener is not started, you need to use the lsnrctl start command to start the listener.

3. Check Oracle error log

If Oracle fails to start, we should check the relevant error log file. On Unix/Linux systems, the error log files for the Oracle database are usually located in the $ORACLE_HOME/diag/rdbms/<DB_NAME>/<SID>/trace directory, where <DB_NAME> is the database name, <SID> is the database name and instance name.

In this directory, we can find a file named alert_<SID>.log, and this file contains the latest Oracle error and warning records. We can understand the specific reasons for Oracle startup failure and find solutions by viewing the error information in the log file.

4. Modify Oracle parameters

Many parameters of the Oracle database can be configured. If these parameters are configured incorrectly, they may cause Oracle to fail to start. Checking the Oracle parameter configuration and making necessary changes may help resolve this issue.

You can check the Oracle parameters by viewing the Oracle parameter file (usually $ORACLE_HOME/dbs/init<ORACLE_SID>.ora), and then adjust it as needed.

For example, if error ORA-27102: out of memory occurs, you may need to increase the system shared memory parameters to a size appropriate for your operating system.

In short, whenever Oracle fails to start, you need to check carefully. The situations listed above are the most common reasons for Oracle startup failure. For any situation, we have the ability to make corresponding repair measures. The ultimate goal is to ensure that the Oracle database can start normally and maintain stable operation.

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