SAP Note 14881 - External number ranges for storage unit number

Symptom:

Number ranges are defined for the storage unit number and are flagged as external. Despite this, the system rejects these external storage unit numbers with an error message ("External assignment of numbers from an internal number range not supported").
Alphanumeric storage unit numbers are used.

Cause and prerequisites

The "external" indicator in the number range definition is ignored. The check is performed for all the number ranges defined.
The only external numbers that are accepted are those that do not appear in a number range.
If you use an alphanumeric SU number, then a MWMK0001 conversion exit is supported for this.

Solution

Only define "internal" number ranges.

1. If you want to exclude certain numbers for external number assignment, define an (unused) internal number range for those numbers.

2. If you want to allow the use of all numbers that do not appear in an internal number range for external number assignment, only define the internal number ranges you actually use.

To use alphanumeric SU numbers, you must set the SU conversion exit to 3 in Customizing under "Warehouse Management -> Warehouse Units -> Master Data -> Define Number Ranges". The Customer Exit MWMK0001 must also be set. Refer to the related documentation. The conversion exit consists of 4 function modules that must be programmed on a customer-specific basis. However, all modules must contain at least one input parameter assignment to the output parameters.

Additional key words

MWMK0001, alphanumeric storage unit number, conversion exit,
L3 212, L3212