MDAC 2.5 SDK - ODBC Programmer's Reference
Chapter 13: Descriptors

Consistency Check

A consistency check is performed by the driver automatically whenever an application sets the SQL_DESC_DATA_PTR field of the APD, ARD, or IPD. Whenever this field is set, the driver checks that the value of the SQL_DESC_TYPE field and the values applicable to the SQL_DESC_TYPE field in the same record are valid and consistent.

The SQL_DESC_DATA_PTR field of an IPD is not normally set; however, an application can do so to force a consistency check of IPD fields. The value that the SQL_DESC_DATA_PTR field of the IPD is set to is not actually stored and cannot be retrieved by a call to SQLGetDescField or SQLGetDescRec; the setting is made only to force the consistency check. A consistency check cannot be performed on an IRD.

For more information on the consistency check, see SQLSetDescRec.