Application Object Layers (Dynamics Ax 2012)

I’m going to explain the layers system in Dynamics Ax 2012. I will make some quotations from Microsoft official site about the Application Object Layers and try to explain by adding my own notes.

Application object layers hold everything that is displayed in the Application Object Tree (AOT).  Layers are a hierarchy of levels in the application source code that enable you to make modifications and additions without interfering with the application objects in the next lower level. When you make an object modification on one level, the modification overshadows the object on a lower level. 

For example, when you edited an object on a level, changes made are stored on that layer. 

If you want to turn to original object, you can just delete the object on modified layer.

You can see which layer are you working on by the bottom right corner of the Axapta window in the development workspace (Ctrl+D).

System standart lowest level is SYS layer and upper level is USR layer.

Layers for Dynamics AX 2012 are explained below;

   

Layer	Description
SYS	The standard application is implemented at the lowest level, the SYS layer. The application objects in the standard application can never be deleted.
GLS	When the application is modified to match country/region specific legal demands, these modifications are saved in a separate layer, the GLS layer. If an application object, for example, a form, is modified in the GLS layer, the modifications are saved in the GLS layer only and the modified version of the form is used.
FPK	The FPK layer is an application object patch layer reserved by Microsoft for future patching or other updates.
SLN	The solution layer is used by distributors to implement vertical partner solutions.
ISV	When an Independent Software Vendor (ISV) creates their own solution, their modifications are saved in the ISV layer.
VAR	Value Added Resellers (VAR) can make modifications or new developments to the VAR layer as specified by the customers or as a strategy of creating an industry specific solution. Such modifications are saved in the VAR layer.
CUS	The supervisor or administrator of an end-user installation might want to make modifications that are generic to the company. Such modifications are saved in the CUS (CUStomer) layer.
USR	End users might want to make their own modifications, such as in their reports. These modifications are saved in the USR layer.

Three customer groups have an interest in adding and modifying application objects:

• Application developers who create the standard application.
• Business partners.
• End users of Microsoft Dynamics AX.

Each layer is saved in a separate file that is named Ax<layer>.aod, for example, Axsys.aod for the SYS layer, Axsl1.aod for the SL1 layer, and so on. The .aod extension is an acronym for Application Object Data.

Each layer has a corresponding patch layer that can be used to incorporate updates to your application or to store conflicts when you import models into a layer.

Sources

https://msdn.microsoft.com/en-us/library/aa851164.aspx

https://msdn.microsoft.com/en-us/library/aa891248.aspx