AIFs were written to provide the intended users fast and quick access to underlying layers with minimal checking. Comparing AIFs to intrinsics, intrinsics are supposed to provide secure access. Fast vs Secure has always been a debated in the AIF team. Most of us who have worked on the AIFs for a while have been convinced that the higher performance is valued more by the software vendors. We tend to design AIFs which do minimal checking. After working with some of the AIF users, this belief of mine has been strengthened by the MPE OS knowledge of these users. Quoting a line from AIF manual, " MPE/iX Architected Interface Facility products are available for purchase by any third party developer. Although other audiences can benefit from using AIFs, they should have a sufficient level of technical sophistication". AIF:PE being a complex product compared to AIF:OS, the user better know what they are doing. However I believe that the AIF:OS user community is undergoing a change as they are getting wider usage now. This brings a dilemma for the AIF developer whether to continue writing AIFs which do minimal checking or make them more secure. It is always good to hear from the users of the product, so let us know. narinder AIF team