Oracle Event Triggers Tutorial

Introduction to Event Triggers

Event triggers in Oracle are special types of triggers that respond to system-level events such as user logins, schema modifications, and database startup or shutdown. This tutorial will guide you through the creation and management of event triggers in Oracle.

Creating Event Triggers

Event triggers can be created to execute custom logic in response to specific events. Here are the steps to create an event trigger:

1. Database Startup Trigger

This example demonstrates how to create a trigger that logs a message whenever the database starts up.

-- Create a trigger for database startup
CREATE OR REPLACE TRIGGER log_startup
AFTER STARTUP ON DATABASE
BEGIN
    INSERT INTO system_events (event_type, event_time)
    VALUES ('STARTUP', SYSDATE);
END;
                

2. User Login Trigger

This example shows how to create a trigger that logs user login events.

-- Create a trigger for user login
CREATE OR REPLACE TRIGGER log_login
AFTER LOGON ON DATABASE
BEGIN
    INSERT INTO user_logins (username, login_time)
    VALUES (SYS_CONTEXT('USERENV', 'SESSION_USER'), SYSDATE);
END;
                

3. Schema Modification Trigger

This example illustrates how to create a trigger that logs schema modification events.

-- Create a trigger for schema modifications
CREATE OR REPLACE TRIGGER log_schema_changes
AFTER CREATE OR ALTER OR DROP ON SCHEMA
BEGIN
    INSERT INTO schema_changes (change_type, change_time)
    VALUES (ORA_DICT_OBJ_TYPE, SYSDATE);
END;
                

Managing Event Triggers

Managing event triggers involves enabling, disabling, and dropping triggers as needed.

Enabling and Disabling Triggers

Triggers can be enabled or disabled using the ALTER TRIGGER statement.

-- Disable a trigger
ALTER TRIGGER log_startup DISABLE;

-- Enable a trigger
ALTER TRIGGER log_startup ENABLE;
                

Dropping Triggers

Triggers can be dropped using the DROP TRIGGER statement.

-- Drop a trigger
DROP TRIGGER log_login;
                

Monitoring Event Triggers

Use the following views to monitor the status and activity of your event triggers:

-- View all triggers in the database
SELECT trigger_name, trigger_type, status FROM all_triggers;

-- View specific details of event triggers
SELECT trigger_name, triggering_event, trigger_body FROM all_triggers
WHERE trigger_type = 'AFTER EVENT';
                

Conclusion

Event triggers in Oracle are powerful tools for responding to system-level events. By following this tutorial, you should be able to create, manage, and monitor event triggers to automate and streamline your database operations.