My answer comes in the form of an Email reply to a friend (why bother to rewrite a prefectly good answer).Please feel free to abuse my answer if you think it deficient, but you better be posting your own alternatives if you do so.The most flexible solution and oldest is #1, the newest solution is #3.
I have been asked several times recently, how to create "dynamic" views such that a view can be created using "variables".
Now I see this question asked on the Ora Faq message board, so I thought maybe this is worth posting as an article, so here it is.
A maintenance mode check is included in the default middleware stack for your application.
If the application is in maintenance mode, a While your application is in maintenance mode, no queued jobs will be handled.
Each option is documented, so feel free to look through the files and get familiar with the options available to you.