Not enough capacity in current optimization period

What causes this issue?

The splitting of the orders in the period must be terminated as not
enough capacity is available.

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?

Choose a larger period or deallocate several orders.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.