Oracle By Example (OBE) has a series on the Oracle Database 2 Day DBA guide. This OBE steps you through the tasks in this section, and includes annotated screenshots.
To view the Monitoring and Tuning the Database OBE,enter the following URL in your web browser:
https://apex.oracle.com/pls/apex/f?p=44785:24:0::NO:24:P24_CONTENT_ID,P24_PREV_PAGE:6290,1