Asynchronous call to web servie using pl/sql

Question

1) How do I make an aynschronous call uisng pl/sql. I am currently using utl_http.
But it is expecting me to get repsonse using utl_http.get_response.
Is there anyway I can make asynchronous call to web service? Please give me examples if any.

Answer 1

Web services are NOT asynchronous as the HTTP application protocol is not asynchronous. A web service cannot (as an sync callback event) initiate a call to the web browser (client app) - as the web browser does not have a tcp listening endpoint. The web service must respond using the EXISTING tcp session established via a connect() call from the browser.
PL/SQL code executes in a dedicated or shared server process. Execution is serialised. So asynchronous calls are not supported and non-existent. Again, async processing requires some from of notification (callback event, message handler or signal interrupt handler) to inform the main process  (while it is executing code), that the async call has completed.
And this does not exist in PL/SQL processing for very good reasons. (Oracle would have been one of the most unstable products on the market if it did support async PL/SQL processing, as 99% of developers would not understand how to use it correctly, and would have severely violated the fundamental concurrency and MVCC principles)
What can be done via PL/SQL (and SQL) is parallel processing - not to be confused with async processing. The API in PL/SQL to use for that is DBMS_PARALLEL_EXECUTE. You can also self roll this using DBMS_JOB or DBMS_SCHEDULER.
No default IPC exists for inter process communication between parallel processes. If IPC is needed, it needs to be manually coded using a standard SQL table (where row locking provides for mutexes and semaphores), or something like DBMS_PIPE.