Hi,

>I'm migrating from Koha 2 to 3 and the field studentnumber of the table borrowers has gone?
reading the code of update22to30.pl the answer is yes.


 243     my %uselessfields = (
 244     # tablename => "field1,field2",
 245         borrowers => "suburb,altstreetaddress,altsuburb,altcity,studentnumber,school,area,preferredcont,altcp",
 246         deletedborrowers=> "suburb,altstreetaddress,altsuburb,altcity,studentnumber,school,area,preferredcont,altcp",
 247         items => "multivolumepart,multivolume,binding",
 248         deleteditems => "multivolumepart,multivolume,binding",
 249         );

> It should be now on a patron custom type?
Yes, but data from borrowers.studentnumber don't migrate.

If you need to migrate data from borrowers.studentnumber to a specific patron attribute
you need to write and ad hoc script.
About patron attributes see: http://translate.koha-community.org/manual/16.05/en/patronattributetypes.html

Bye