Instance creation fails with default instancetypeid

If MARC record comes without instanceType (field "336") we have to put default instancetype to Instance(that is spawned by this record) to pass the validation of the mod-inventory. The instancetype is required field and mod-inventory receives an Instances only with instanceType defined.

Since database constraint was added on the instanceType field (in mod-inventory-storage), we have to use the only instanceType that lives in mod-inventory-storage to save Instance successfully.

When incoming MARC record comes without instanceType, which one value we have to take as default and put to an Instance while mapping?