FYI

Just tried OpenCobol with DB2 v9 (64-bit, AMD64 version) and can confirm
that it works and no changes or header tweaking are required.
The only thing is that for precompiler you should put "target ANSI_COBOL",
otherwise it will generate CALL-CONVENTION, i.e.
db2 prep testdb2.sqb bindfile target ANSI_COBOL

Regards,
Sergey