Lesson 2	What to monitor?
Objective	List terms to monitor on a regular basis.

What to monitor

When managing an Oracle database, you should be monitoring a variety of items on a regular basis. The table below lists the items and the reasons they need to be monitored:

Item	What to monitor
Database alert log	This is a text file to which Oracle writes serious error messages. Oracle also generates log entries for significant events such as database startup and shutdown.
License compliance	Most Oracle licenses specify a maximum number of users. Are you exceeding that number?
Disk space	How much are you using currently? How much free space do you have? When will you run out of space?
Buffer cache hit ratio	Do you have enough memory allocated to the database buffer cache?
Dictionary cache and library cache hit ratios	Do you have enough memory allocated to the shared pool?
File I/O statistics	Is your I/O load evenly distributed across multiple disks?
Redo logs	Do you have enough redo log files so that users aren't forced to wait while one is archived? Are you experiencing buffer contention?

What are Dynamic Performance Views in Oracle?

In Oracle database, dynamic performance views (also known as "v$ views") are a set of views that provide real-time information about the current state and performance of the database. These views are built on top of memory structures and background processes in the database, and they are updated continuously as the database changes.
There are many different dynamic performance views in Oracle, and they provide a wide range of information about the database. Some examples of information that you can get from dynamic performance views include:

Current sessions and active transactions
Wait events and locks
Memory usage and other resource utilization statistics
Performance statistics for various database components, such as the buffer cache, the redo log buffer, and the shared pool

Dynamic performance views are an important tool for database administrators, as they allow you to monitor the performance and health of the database in real-time. They are often used in conjunction with other monitoring tools and techniques, such as the Oracle Enterprise Manager console or custom scripts and tools.

Dynamic Performance Views

Monitoring many of these items involves selecting data from Oracle's dynamic performance views. Dynamic performance views are the ones owned by the user named SYS and have names that begin with V$. In fact, DBAs commonly refer to these as the "V$ views" (vee-dollar). Oracle implements a large number of V$ views, and the information that they return constantly changes to reflect changes in the state of the database over time.
In the next lesson, I will describe the contents of the alert log.