You are right, I need an API that works with any version of DB2 UDB
client (version 5, 6, 7, or 8). The application does not know in the
advance what DB2 UDB client or server version is used and can not be
restricted in the advance.

I have a DB2 8.1.6 and the db2ApiDf.h is here but this API is not in
the db2ApiDf.h. Anyway, seems that this is just a new version of the
sqledgne - Get Next Database Directory Entry API, so it would,
perhaps, return same value of the dbtype (same name as dbtype in the
sqledinfo used in the sqledgne).

The bigger problem with this API (db2DbDirGetNextEntry - Get Next
Database Directory Entry) is that you have to provide a versionNumber
(Input Specifies the version and release level of the structure passed
in as the second parameter pParmStruct) as first parameter. Imagine
that, in order to obtain a dbtype (Database manager release
information) you have to provide a versionNumber (Input Specifies the
version and release level of the structure passed in as the second
parameter pParmStruct). Congratulation to DB2 API designers. You are
great. Please give me a value and I will design an API that is going
to return that value. And I will assign a smart advisor that is going
a help people in the public newsgroup to use that API. Seems that
there is still somebody enough smart in the DB2 team who hides that
API, so we can not find it yet.