How is Oracle AS Portal page gets rendered to users?

When a client requests an OracleAS Portal page, many Oracle Application Server components must respond to various parts of the request:

1. The client browser requests a portal page. OracleAS Web Cache receives this request.
2. OracleAS Web Cache forwards the request to the Oracle HTTP Server
   
3. Oracle HTTP Server forwards the request to the Portal Services
4. The PPE (Parallel Page Engine), which is part of the Portal Services, retrieves the portal page definition.The page definition contains information about the portlets on a page and their layout.
5. First, it tries to get the cached copy of the definition from OracleAS Web Cache.
6. If there is a cache miss in OracleAS Web Cache, it checks if the portal cache has a valid cached copy
7. Finally, if no valid cached copy of the definition exists, then the OracleAS Metadata Repository generates a page definition from data in the portal repository
8. The PPE parses the page definition.
9. For each portlet on the page, the PPE checks if a cached copy of the portlet content exists in the portal cache or OracleAS Web Cache and then forwards a request to the appropriate provider, through Oracle AS Web Cache
10. Each provider either validates the cached portlet or generates content for the portlet. Web providers return this directly to the PPE using HTTP/S. Database (DB) providers return the results to the PPE through OracleAS Web Cache, Oracle HTTP Server, and Portal Services, using HTTP/S or SOAP
11. The PPE aggregates the content into a single page. This page is sent to Oracle AS Web Cache.
12. OracleAS Web Cache returns the final page to the client browser.