In https://koha-community.org/manual/23.05/en/html/cataloging.html#added-entry-elements-label it is said that 942$2,$6 and $c is used in UNIMARC installation in the same way as MARC21 It is not the case in my (unimarc) library, and it is not what is written in the wiki https://wiki.koha-community.org/wiki/Holdings_data_fields_(9xx) Is it hardcoded somewhere in Koha ?
The wiki page linked doesn't have any information about 942 use in MARC21, so I think the information about UNIMARC missing there is not really saying much. I think the important bit would be verifying the mappings in the default UNIMARC frameworks as they are shipped with Koha now and the default indexing.
Indeed you are right Koha/installer/data/mysql/en/marcflavour/unimarc/mandatory/unimarc_framework_DEFAULT.sql defines 942$0 : 'Koha issues (borrowed), all copies' 942$2 : 'Source of classification or shelving scheme' 942$6 : 'Koha normalized classification for sorting' 942$c : 'Koha item type' 942$s : 'Serial record flag' But the french version only defines 942$0 Koha/installer/data/mysql/fr-FR/marcflavour/unimarc_complet/Obligatoire /framework_DEFAULT.sql The other fields (Koha item type...) are in 099 And french vendors (at least Biblibre) use their own templates based on the fr-FR template. I wonder why french people have used 099 instead of 942
I'm writing to the french community to know more about this divergence