Microsoft Dynamics AX is fully
customizable. Most of the code used by Dynamics AX is written in X++ and it is
visible and editable in the AOT. This feature provides developers with the
ability to add, remove, and even replace intrinsic Dynamics AX functionality
within the system.
Some developers are more cautious
than others, some are more detailed than others, and some of them spend more
time and resources in testing new changes they made to the system. But after
all, we are all humans and we can make mistakes. Having this amount of power, a
developer could potentially make the system unusable.
Microsoft’s approach to this issue
was to introduce the concept of layers. A layer is a hierarchical location
where code resides. From left to right, these are the most common layers
available in a standard Dynamics AX system:
SYS > GLS > FPK > SLN >
ISV > VAR > CUS > USR
Each layer is completely independent
of the other layers. You specify which layer to connect to when setting up the
AX client profile.
The bottom layer will be the SYS
layer and this is where the standard application code is located, and is only
accessible by Microsoft. Other layers like ISV (Independent Software Vendor),
VAR (Value Added Reseller) can be accessed by entering keys that Microsoft
provides for each layer except USR (User) which does not require a key.
So the objective of the layers is to
provide developers with the option to modify Microsoft’s code but only in one
of the layers the developer has access to.
Every time a developer makes a
change to a Dynamics AX object in the AOT, a copy (version) of the object is
taken from a system layer to the layer which the developer is connected to. If
there are multiple versions of the same object in different layers, then the
top layer will take precedence and will be used.
Let’s use an example:
Standard Dynamics AX comes with a
table named ALPHABET that consists of columns: A, B, and C. If there are no
changes made in other layers then the end user will see the table exactly as in
the SYS layer.
If a developer logs on to Dynamics
AX to the VAR layer and adds column D to the table, this is what happens.
Finally if a developer in the USR
layer decides to remove columns B and C, this is how the table definition will
be seen by the end user.
As you can see, the top layer will always be
used, and in this case, it will not matter if you keep adding columns to the
table definition in the VAR layer as those new columns won’t be available to
the end user, as the USR layer takes precedence.
Reference : http://www.erpsoftwareblog.com
Regards,
Sathish
