Release note: Requirements and availability 3.0
Description
Locking logic in Release 3.0
Release 3.0 provides a new locking logic across all Logistics applications. This new form of locking a material for processing allows more than one user to access a material almost simultaneously, without causing the results of the availability check to be inaccurate.
The lock is activated when the system carries out the availability check. It ignores the lock which has been set until this point at material and plant level (MARC). This means that all goods movements in inventory management and SD are possible simultaneously. There is, however, the risk that the stocks for which availability is checked are incorrect, in particular if there are simultaneous goods issue postings for the same material.
If goods movement transactions (e.g. manual goods issue) may be used at the same time as SD/PP functions which call up the availability check, then the availability check must be activated for the appropriate movement types. This guarantees data consistency. The goods issue posting in the SD delivery is not in this category of goods movements because the requirements existing for the delivery already reserve the relevant stock. The same applies to all further transactions for which stocks are reserved and, for example, initiate a withdrawal.
Procedure for the new locking logic
The new lock functions as follows:
At the beginning of the availability check, the material used is locked
exclusively in the plant specified - as was the case until now. Then the check
is carried out: in SD this can be the availability check according to ATP
(available to promise) logic or a forecast. Once the check has been completed,
the corresponding confirmed quantities have a shared lock and the exclusive
material lock is removed. This shared lock serves the purpose of informing
other parallel sessions of all business transactions currently in process if
they are accessing the same combination of material and plant. The
availability overview which you can call up from the SD document displays
these temporary lock records. You can also find them in the list of lock
entries. A possible dialog takes place (for example, via the availability
control screen) when these lock records have been created.
By means of this procedure, the lock time is reduced to the length of the runtime of the availability check. If another user comes across the above mentioned exclusive lock, the system makes five attempts to lock the material exclusively for this transaction. After each failed attempt, the process waits approximately one second before starting the next attempt. If the last attempt fails, the system issues a corresponding message and terminates the check. The transaction is not confirmed, the long text of the message informs the user that the availability check must be called up again if the transaction is to be confirmed. If a planning material is available, it will also be locked according to the same rules.
The manual procedure for updating backorders locks the material exclusively for the whole processing time. This means that the availability check cannot be carried out during this time. Rescheduling, however, which represents a normal form of order processing, works with the new lock and allows competitive transactions.
The lock entries for each user are reset at the end of the transaction - that is when the transaction is terminated without saving. If the processed transaction is saved, the lock entries are reset after the database is updated. The time lapse between this update and the moment at which the lock entries are reset is minimal (of the order of a millisecond). The changed database records and the lock records exist in parallel during this time. This means that for this short length of time, the system could confirm for a further transaction a smaller quantity than is actually available. As the length of time is, however, extremely short, the probability that this will occur is very low.
Change system parameters in customizing
You activate/inactivate this new locking logic when maintaining checking groups for the availability check. The conventional lock remains active if it is configured as such in Customizing. If both options are active, the new locking logic applies.
For information on maintaining checking groups, refer to 
Define checking groups in the Implementation Guide. For details
on maintaining the conventional lock for materials, see
Define material block for other users in the Implementation
Guide.