Oracle monitoring db status I am looking for a way to monitor Oracle database status (health) via PHP script executing SQL query. There are system variables containing actual number of connection, sessions, work load, etc...

How I can access to those values: via regular SELECT statement, or built-in stored procedure, or it need to be custom build stored procedure...

How I can detect, after I get those values, is it a normal, heavy, extreme work load. What are the criteria?
What is 'normal' will depend on your situation. An OLTP database and a warehouse will have very different usage profiles.

If you use a connection pool, then you probably don't expect to see a wide variation in the number of connections or sessions. Such a change would indicate a problem.

Generally you are best off looking for dramatic changes in your measures.

Grab SQL Developer 3 Early Adopter edition from the Oracle website. Check out some of the system reports, and look at the underlying SQLs.