I've done earlier blog posts on handy mechanisms in Classic 3270 interface, like ASF (Automated screen facility) and XLF (exception log facility). XLF provides you with a mechanism to gather and log classic interface exceptions.
A recent technote came out with a description of how to log classic exceptions to a DASD file. You might do this if you want to maintain an ongoing log of classic exceptions, or if you want to interface these classic exceptions to a another tool, such as 3rd party automation.
This is a good description of setting up XLF. Here's the URL: