Hi @tiyok,
Ah, I’ve just realized, that that column was defined as “I4” i.e. as “int” in OJS 2.4.8 but in OJS 3.0 as “I2” i.e. “smallint” :-\ Could you maybe change it for yourself and test it? Change this line https://github.com/pkp/pkp-lib/blob/master/xml/schema/metrics.xml#L47 in your lib/pkp/xml/schema/metrics.xml file so that type="I4". Then restore the backup and try the upgrade again. Please let us know, if that worked then.
Best,
Bozana