User &2 is creating a delivery for reservation &1

What causes this issue?

For a delivery you have selected material components for reservation
&v1&. User &v2& is creating a delivery for the same reservation.

System Response

Processing is not continued

How to fix this error?

Try again when user &v2& has finished the transaction.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.