No operative delivery schedule created (Requirement quantity zero)

What causes this issue?

You have reduced the requirement quantity of a line of a scheduling
agreement delivery schedule to zero and wish to create an operative
delivery schedule.

System Response

The operative delivery schedule was not created (which means the
requirement will not be cancelled) because:
The requirement quantity in the last-transmitted operative delivery
schedule already amounted to zero and thus it is unnecessary to inform
the vendor of a change in requirements, <ZH>or</>
No operative delivery schedule has yet been transmitted and therefore
it is unnecessary to inform the vendor of a requirement for a zero
quantity

How to fix this error?

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

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.