/usr/lib/mono/4.5/IBM.Data.DB2.dll is in libmono-db2-1.0-cil 4.6.2.7+dfsg-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/mono/4.5/../gac/IBM.Data.DB2/1.0.0.0__7c307b91aa13d208/IBM.Data.DB2.dll