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Lesson 3 The alert log
ObjectiveDescribe the contents of the alert log.

Alert Log Information

The alert log is a text file used by Oracle to record significant events while a database is running. The log is written in chronological order, and the most recent information appears at the bottom of the file. Alert logs contain the following types of information:
  1. A record of all redo log switches.
  2. Log entries that record each startup and shutdown. Startup entries include lists of all initialization parameters having values other than their default.
  3. Messages about internal errors related to problems within the Oracle software.
  4. Messages about other significant errors.
  5. Records of changes to the database's physical structure.

alert log

  1. What is the rule to find the location of the Oracle alert log.
  2. I am on an Oracle 11g server and I cannot locate the alert logs.
  3. How do I quickly find the location of the Oracle alert logs on an unfamiliar server?
Answer: The Oracle alert log location is determined by
  1. the background dump destination and
  2. specified by the background_dump_dest parameter.
  3. You can display the location of the alert log directory using the following SQL*Plus command:

SQL > show parameter background

Some of the information in the alert log is routine in nature and some is not. You should check the alert log on a daily basis and many DBAs check it more frequently to see if any errors or unusual events have been recorded. Then you need to act on that information.
In the next lesson, you will locate the text file containing the alert log for your database.

What type of information should I search for in the Oracle alert log?

The Oracle alert log is an important source of information for diagnosing and troubleshooting problems with the database.
Some examples of the type of information that you might search for in the Oracle alert log include:
  1. Error messages: The alert log will record any errors that occur while the database is running, such as ORA-errors, which are standardized error codes used by Oracle.
  2. Alert thresholds: The alert log will record any alerts that are triggered by the database, such as when a table or index becomes fragmented, or when a tablespace runs out of space.
  3. Database startup and shutdown: The alert log will record messages related to the startup and shutdown of the database, including any errors or issues that occur during these processes.
  4. Configuration changes: The alert log will record any changes that are made to the database configuration, such as changes to initialization parameters or the addition or removal of database files.
  5. Performance issues: The alert log may also contain information about performance issues, such as long running queries or waits on certain types of locks.
It is a good idea to regularly check the alert log for any new messages or errors, and to address any issues that are identified as soon as possible to prevent them from escalating into larger problems.

Routine Monitoring - Quiz

Click the Quiz link to answer a few questions about routine monitoring.
Routine Monitoring - Quiz