Input parameter cannot be define; template available

What causes this issue?

You tried to add a new allocation for an input parameter.

System Response

Allocations to input parameters are not allowed for single components
when a template has been allocated.

How to fix this error?

First delete the template allocation for the input parameter, and then
add a new allocation for the input parameter.

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.