All Transactions are Running Slowly (Oracle)
You may encounter situations where all applications appear to be performing poorly.
The questions to ask should include:
If the answers to these questions lead you to believe there is a system-wide performance problem, the following topics may help you determine the cause.
Monitoring the Shared SQL Area (Oracle)
Checkpoint Monitoring (Oracle)
Checking the Optimizer Mode (Oracle)
Keep in mind that a single poorly-performing application may use considerable system resources causing other non-related applications to falter. For this reason, it is a good idea to also review the subjects discussed in other sections when tracing down a system-wide problem.