IRule Redirect URL to other URL for maintenance

For your policy you do need a negative matcher for /app_offline_abd.htm, or it will give you a redirect for that page, too. That's condition 1 in my policy foo:

                1 {
                    http-uri
                    path
                    not
                    values { /app_offline_abd.htm }
                }

Other than that, your policy looks right to me.