There is a change in the default behaviour of handling JSP cache
in R12 as opposed to 11i. Remember, JSPs were handled by Apache
Jserv engine in 11i and is being handled by OC4J (10.1.3 AS) in R12.
In 11i, when we clear cache ($COMMON_TOP/_pages) and try to
access JSP pages, it gets automatically recompiled. However, this
is not the case in R12 by default.
So, in an R12 instance, if you clear _pages and restart apache,
you will only get a blank screen since AppsLocalLogin.jsp wouldn’t
get compiled by default. You will not even see a new _pages directory.
To overcome this, as per Oracle, whenever JSP cache is cleared, we have to run
“ojspcompile.pl” to recompile ALL jsp pages in the Application.
This will take roughly around 15 to 20 mts. However, in the real world
(atleast in the pre-production stage) this is not affordable.
The solution to this is to change the XML file parameter
s_jsp_main_mode to a value of “recompile” from the default value of
“justrun” and run autoconfig. JSP pages will be recompiled automatically
after this change.
Source : http://oraclepitstop.wordpress.com