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.
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.

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
This is described in greater detail in the section entitled
The Update Process.