Changes to HU & were not successful

What causes this issue?

The system could not change the handling unit.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Is the handling unit identification number correct?
Does the HU to change already exist? (see table VEKP)
Is the handling unit locked by another user?
Is the data to change (such as quantities) consistent?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.