Lesson 1

Now that we covered the basic concepts behind Oracle performance tuning, it's time to look at the single most important file on any Oracle server, which is the alert log. The Oracle software keeps this historical log of all important database messages. Understanding this alert log is fundamental to understanding Oracle performance tuning. The alert log contains many important types of information regarding the health of your Oracle database. The alert log is a common repository file for all messages that are produced in the Oracle software. Every database on a server has its own alert log, which is kept as a standard flat file on the server.

By the end of the module, you will be able to:

1. Find the location of the alert log on any Oracle server
2. Identify the main types of alert log messages
3. Identify specific informational and task termination messages
4. Recognize severe errors in the alert log and identify the correct remedy
5. Monitor the alert log for serious conditions

The Oracle alert log file is a file used by the Oracle database to record important messages and errors. The alert log file is also known as the Oracle alert log, or just the alert log. The alert log file serves several important functions:

1. It records messages and errors generated by the Oracle database and its background processes. These messages and errors can include information about problems with the database, such as data corruption or hardware failures.
2. It records information about the startup and shutdown of the Oracle database and its background processes.
3. It records information about events that occur within the database, such as the creation or deletion of database objects or the execution of certain SQL statements.
4. It provides a record of database activity that can be used for debugging and performance tuning.

The alert log file is located in the Oracle diagnostic destination, which is specified in the DIAGNOSTIC_DEST initialization parameter. By default, the alert log file is named "alert_SID.log", where SID is the database identifier (DBID). The alert log file is written to by the Oracle database and its background processes, and it can be viewed using a text editor or other tool.
Now let us get started by learning to find the alert log on any Oracle server.