An update is divided into different modules (see also 
Update Request). Each module corresponds to an update 
function module. 

There are two types of module.

The SAP System makes a distinction between primary, time-
critical (V1) and secondary, non-time-critical (V2) update 
modules. The system also supports collective runs for 
function modules that are used on a regular basis. 

This distinction allows the system to process critical 
database changes before less critical changes.

V1 modules describe critical or primary changes; these 
affect objects that have a controlling function in the SAP 
System, for example order creation or changes to material 
stock. 
V2 modules describe less critical secondary changes. These 
are pure statistical updates, for example, such as result 
calculations.
The V1 modules are processed consecutively in a single 
update work process on the same application server. This 
means that they belong to the same database LUW and can be 
reversed. Furthermore, V1 updates are carried out under the 
SAP locks of the transaction that creates the update (see  
The SAP Lock Concept). This ensures that the data remains 
consistent; simultaneous changes to the objects to be 
updated are not possible.

All V2 updates are carried out in a separate LUW and not 
under the locks of the transaction that creates them. If 
your SAP System contains a work process for V2 updates, 
these are only carried out in this work process. If this is 
not the case, the V2 components are processed by a V1 
update process.

All V1 modules of an update must be processed before the V2 
modules.