"Insert on existing update" - updates pKey fields

Hello, all

I have a question: why command "insert on existing update" updates not only data fields, but the key fields as well?

Here is my use case:

The database is no case sensitive

A record is entered with alphanumeric key in lower case.

Then an external application executes command "insert on existing update" and sends the key in upper case. The record is updated and so is the key field.

This would not be a real issue, if the table was not part of an upload publication. The system notices change in the key and disallows the update.

Is there a parameter, when I can set that during "insert on existing update" only the non-pkey fields will be updated?

Thank you

Arcady