From Support Wiki
Oracle OLE DB Provider and truncation of String parameters in PL/SQL procedures.
Stacy Stillwell – Gupta Technologies LLC
This bulletin is intended for developers investigating the move from the Oracle native router to the Oracle OLE DB Provider. Developers that are migrating to OLE DB Provider who are using PL/SQL Calls with String OUTPUT parameters will find that the values are truncated.
The problem is two-fold. There is a known Oracle defect, number 1726980, which is fixed in Oracle’s 9.2.x OLE DB Provider. There is also a known GUPTA defect which will be fixed in TD 2.1 PTF 2 and TD 3.0.