Revised layer version in DAX 2009

In Microsoft Dynamics AX, a layer system is used to manage application objects. A single index file named Axapd.aoi automatically makes sure that the top-level version of an application object is always used. The USR layer is the top layer and the SYS layer is the bottom layer. The following illustration shows the 10 Microsoft Dynamics AX layers.

For example, when a user opens a form, a check is made to determine whether there is a USR layer version of the form. Next, a check is made to determine whether there is a CUS layer version, and so forth, until the SYS layer version is used.

Most application objects, such as tables, fields, indexes, enum types, and extended data types have unique application object ID numbers in addition to names. Microsoft Dynamics AX uses an application object ID number series corresponding to the layers, as shown in the following picture.

When an application object is created, Microsoft Dynamics AX automatically manages the application object ID and assigns a new ID. If you modify an existing object, the application object keeps its original ID and is not assigned a new ID in the same layer. If you move an application object to a new layer, a new ID is automatically assigned.

Note- If you delete the layer file, you should also delete the index file to make the system regenerate it.