Topic overview
This article explains the most important processes that can lead to storage location reservations. You will also learn how storage location reservations are executed and how they affect other processes and applications. The applications used and the related fields, actions, and procedures are described in detail in separate articles.
Definitions of terms
Storage location
A storage location is the exact point in a warehouse where items can be stored. A storage location within a warehouse always lies in a warehouse zone and is determined precisely on the basis of a row, a level, and a storage location number. Each storage location has a storage location category that establishes the use of the storage location. The availability of storage locations is essential for storage location control.
Storage location reservations
Storage locations can be reserved for future receipts and issues. Inventory in unstructured warehouse zones (except the inventory difference zone) is also reserved for future receipts and issues. If the storage location includes has more than one storage unit, slots will be reserved. Storage location reservations are created, for example, when inventory orders are created or when a storage location or an unstructured warehouse zone has been explicitly specified in an inventory requisition. This prevents the sum of the actual inventory and all open reservations from becoming negative.
Storage location reservations
The quantity of future receipts and issues is recorded on a storage location through storage location reservation. The storage location prevents the generation of inventory orders for put-away that will result in exceeding the maximum
inventory for a storage location. In the case of withdrawal, the storage location reservation prevents double withdrawal of the same inventory.
In unstructured warehouse zones, quantities are reserved in the same manner; the general term Storage location reservations also covers reservations in unstructured warehouse zones as a special case of storage location reservations.
In the case of withdrawal from an unstructured warehouse zone, the reservation prevents redundant withdrawal. On the other hand, any existing reservations do not affect put-away in an unstructured warehouse zone because a warehouse zone does not know any capacity limitations.
However, in the virtual inventory count difference zone, it makes no sense to apply reservations because this fictitious warehouse zone is reserved only for inventory count postings and inventory count postings without reservations.
Creation of storage location reservations
The following vouchers cause storage location reservations:
- Incomplete inventory requisition with entering of a storage location or an unstructured warehouse zone
- Non-reported inventory order, unless the storage location reservation has already been caused by the inventory requisition
- Inventory posting in a structured warehouse that has not been processed by the corresponding inventory management server. Exception: Correction posting from inventory count
- Incorrect posting from the incorrect inventory posting by entering of a storage location or an unstructured warehouse zone
- Open receipt of goods in a structured warehouse (receipt of goods is already posted, but inventory orders have not yet been generated or have not been generated for the entire quantity)
- Incomplete picking order (for inventories that have been transported through reported inventory orders to the issue of goods zone)
- Undelivered delivery order (for inventories picked in the issue of goods zone)
If the displayed storage location is changed in an inventory order, a storage location reservation is executed for the new storage location. If the reservation is successful, the storage location reservation of the old storage location is subsequently removed and the change is permanently saved. The same applies to an unstructured warehouse zone.
Automatic slot determination and storage location reservation
If it is set for a storage location with storage unit that a slot is to be determined automatically when this specification is missing, the following applies to the storage location reservation:
- The storage location reservations requests are sorted by the system. If, for example, the same storage location was specified twice, once with a slot and once without, then the storgae location reservation request with the slot specification is considered first. Otherwise, it would be possible for the request without the slot specification to assign the slot that is already specified in the second request. The second request would then be rejected as not reservable with an error message.
- When processing storage location reservation requests, the search is carried out in ascending order via the slots of the storage location. The first slot that fulfills the requirement, e.g. sufficient inventory, is selected.
- Withdrawal:
The slot with which the requested quantity can be fully reserved is selected for withdrawal. If several slots of a storage location meet this requirement, the slot whose item has the oldest FIFO date is selected.
Removing storage location reservations
If the inventory management server has processed the inventory postings resulting from the reporting of the inventory order, the storage location reservations are removed again. If an inventory order or an inventory requisition is deleted or canceled with an explicit specification of a storage location or a warehouse zone, the storage location reservations that have been possibly generated for the voucher are removed as well. The reservations of the already picked inventories in the issue of goods zone are also undone upon cancellation of a picking order.
Resetting storage location reservations
If warehouse details are changed in an inventory order, e.g. the storage location is changed, storage location reservations are canceled and made again according to the changed details. If an error occurs when saving these changes, the changes in the inventory order are undone and the storage location reservations are reset.
If the storage location reservations cannot be reset or can only be partially reset, for example due to a storage location reservation made in the meantime by another inventory order, the following workflow event is triggered:
com.cisag.app.inventory.order.LocationReservationRollbackError
It is recommended to check the storage location reservations of the affected inventory order line items immediately and correcting the incorrect data using the Recompilation of storage location-reservations application, as otherwise further incorrect data may occur.
Displaying storage location reservations
Storage location reservations are displayed in graphic form in the Storage location query application. However, only the existence of a storage location reservation is displayed and not the reserved quantities. The reserved quantities can
be viewed in the inventory records on the storage location level (business object: com.cisag.app.inventory.obj.UnitOnhandDetail). The inventories and storage location reservations are item- and identifier-managed therein. The summaryLevel attribute shows the level of consolidation applicable for the record in each case.
The following table describes the attributes that are relevant for the storage location reservation in the business object: com.cisag.app.inventory.obj.UnitOnhandDetail:
| Attribute | Name | Explanation |
| unitOnhand | Inventory record | Reference to the inventory record of the storage location or the slot. |
| item | Item | The item to be transported. |
| identifier | Identifier | If the item is managed by identifiers, this attribute contains the identifier to be transported. |
| outgoingQuantity | Future issues | Quantity of the future issues. This attribute represents the storage location reservation for withdrawals. |
| incomingQuantity | Future receipts | Quantity of the future receipts. This attribute represents the storage location reservation for put-aways. |
| summaryLevel | Level of storage location reservation | The following levels are available:
In the case of the Item total value, |
Preventing negative inventory
Negative inventory in the storage location control can lead to subsequent errors, for example, they can permanently distort the history and thus the results of automatic put-away and withdrawal algorithms, and the wrong transport instructions will only keep on multiplying over the course of time.
Therefore, the occurrence of negative inventory is basically prevented in the storage location control. As a rule, if a process leads to negative inventory (i.e., if the inventory plus open receipt quantities and minus open issue quantities is
negative), it should be canceled.
The rule can also allow for temporary negative real inventory in storage locations without storage units as well as in warehouse zones. However, this can only happen if an equal or a greater open put-away exists in the storage location or in the unstructured warehouse zone. In reality, such a state can occur if an issue posting was processed by the inventory management server before the receipt posting, which is possible in the case of asynchronous working of the inventory management server. The goods have to be already received physically before it could be successfully used. Of course, this means that if the receipt inventory posting has not been generated at all, the put-away process will have to be completed.
Negative future inventories are basically prevented in the storage location control, independently from the customizing setting in Inventory Logistics/Inventories → Allow negative inventory that applies only to inventories at the warehouse level.
However, there is a legitimate way to generate a negative future inventory. The inventory discrepancies are posted without reservations, for example, when booking a negative inventory discrepancy in a storage location where the complete inventory is reserved by an inventory order, a negative future inventory will occur. Due to the fact that this situation can occur with low probability and cannot be prevented, the future inventory will be also controlled when saving
changes of the inventory and reservation data. However, if it does fall below zero by a devious route, a message log entry is generated for this situation and a workflow event com.cisag.app.inventory.NegativeFutureOnhandCreated is sent. The inventory on the affected slot/storage location or in the unstructured warehouse zone should be controlled and corrected because this inventory situation cannot exist in reality and indicates that processes were incorrectly
mapped (for example, already withdrawn inventory was posted once again as an inventory count, etc.).