V1 and V2 Update Modules 
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.
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.
Let us assume that a transaction makes planning changes to a material and balance sheet, and updates two sets of statistics.
Each of these changes is represented by means of an update module (call update function module) in the update request - the two planning changes by a V1 update module (time critical), and the statistical changes by a V2 update module (less critical). (The V1 modules have priority, although the V2 modules are usually also processed straight away).
