Sometimes an APEX application performs worse than expected. This can have many causes, ranging from wrong parameters in the database (for example the SGA allocation) to less-than-optimal queries.
Besides the tools that a DBA has to check the performance and take action according to his findings, a developer also has some options to use in Application Express.
1. In the Apex Admin application there are some reports under the tab Monitor Activity. In the Page Views by View report that is found in the Page Views section, you can see how long it takes a page to load in the browser. Using this it is possible to see which pages take too long to load.
2. By using the Debug option in the developer toolbar, APEX generates a lot of debug information. Using this information a developer can see how a page is built-up in the browser. In front of each line of debug information is a time-stamp. This information allows a developer to analyze what part of a page is causing the delays.
3. It’s possible to let Application Express generate a trace file from the URL. To do this, simply add &p_trace=YES to the URL and call the page again. This generates a trc file in the user_dump_dest directory (find this using show parameter user_dump_dest). This file can also be analyzed to find where the problems may occur.
Offcourse this list is not a complete overview of all tools that are available to analyze performance problems, but I think you can get a good start.