Hi,

Here you have to import the categories to the v15 Db with same external ID as in the previous version. Suppose for importing the product categories, export the categories with needed fields (except parent category) from the first db and import it in the next db with same external ID.

Once the categories are imported in the second db, again export the same categories from db 1 with only parent category information and import it again in the second db, now the parent categories will be updated.

In order to avoid two steps of export, you can export including parent categories in the first step, but don't import it in the second db in the first import, keep the column not to import for the first time and import rest of the data.

Once the first step is done, import the same file again, only parent category this time.

Thanks