bottleneck, throughput, Wait events

1. Removing the major bottleneck (apoint where resource contention is highest)
2. performance problems result from a lack of throughput (the amount of work
that can be completed in a specified time), unacceptable user or job response time (the
time to complete a specified workload), or both.
3. Wait events are incremented by a session to indicate that the session had to wait for an event to complete before being able to continue processing. When a session has to wait while processing a user request, the database records the wait by using one of a set of predefined wait events. The events are then grouped into wait classes, such as User I/O and Network. Wait event data reveals symptoms of problems that might be affecting performance, such as latch, buffer, or I/O contention.