I am new to dba.Please any one clarify my doubts

1)How can you monitor for performance problems in a specific Oracle session? Say an application is slow at displaying a particular page, but the developers aren't able to identify which SQL statments are the culprits. How could you help?

2) Say an application server uses a pool of 20 database connections. They are shared among some hundreds of concurrent users, so each connection is active most of the time. The database is on another machine. How would you use Multi Threaded Server in these circumstances?

3)Here are some categories of parameters for routine monitoring. Can you suggest any more? How would you monitor each?

Disk I/O

Thnanks in advance