Hi, Aida!
UseControlNumber to Use record control number ($w subfields) and control number (001) for linking of bibliographic records. ... I also remember reading something about this not being a good choice if you have serials and if you are planning to catalog articles.
We have serials and catalog articles ("analytics") and this works fine for us (with custom XSLT from ByWater that they are happy to share with the community) and is better than searching for author and/or title due to the often generic titles of serials. Uploading a local cover image is easy-peasy! It can be uploaded to go with an item or at the bib level. We pull cover images from OpenLibrary, so I will often contribute the cover image to OpenLibrary.org so it's more widely available. And why are there more bibliographic frameworks with a MARC21 installation? I'm a Real Cataloger and I have no idea—we use the default framework exclusively. The other frameworks are, IMO, completely unnecessary. I think they are used more often in consortia or really large libraries that may have lots of staff contributing records with very different levels of training and expertise. The differing frameworks/choices of authority records also drive me round the bend—I dream of a day that I can open an Advanced Authority Editor and just key in an authority record. Cheerio! h2 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Ms. Heather Hernandez (she, her, hers) Technical Services Librarian Library catalog: https://keys.bywatersolutions.com/ San Francisco Maritime National Historical Park Research Center 2 Marina Blvd., Bldg. E, 3rd floor, San Francisco, CA 94123-1284 415-561-7032 (office, generally M, W, F, telecommuting Tu,Th) heather_hernandez@nps.gov<https://webmail.lmi.net/src/compose.php?send_to=heather_hernandez%40nps.gov>