Once a record is harvested from an OAI repository, a record is created in Koha. If the record is modified in the source repository, it will be re-harvested and the Koha record will be modified (well, I suppose it is the case...). In most situation this will be fine, but we can have workflows in which the Koha record is modified manually or by a plugin (for example, we can imagine a process which adds an abstract to the record). In that case it could be nice to be able to "protect" the Koha record globally or only for some fields. I have no idea of the best way of doing that.