Application Object Patch Layers
In addition to the eight layers in Microsoft Dynamics AX, each layer has a patch layer. The patch layers are called SYP, GLP, DIP, LOP, BUP, VAP, CUP, and USP.
The patch layers are designed to make it easy to incorporate updates in your current application. The basic idea is that when a minor update or correction is made, it is distributed in a patch file, for example Axsyp.aod. When a patch file is present, the modified objects in the patch file take precedence over the regular objects and are automatically used.
The patch files use the same number series as the regular files use.
The major benefit of the patch layer concept is that you can easily create and distribute an update. for example by using the Internet, without interfering with the existing application. When you subsequently incorporate the update in the regular layer file, you can delete the patch file (Ax??p.aod ) and the index file (Axapd.aoi).