When an access service receives data values as parameters to RPC commands, cursor commands, or dynamic SQL commands, it converts Open Client and Open Server datatypes to default target DBMS datatypes.
In most cases, Open Client and Open Server datatypes directly map to target datatypes, and the service library defines default mapping rules. However, if the defaults are not valid, the CT-Library client specifies the intended target datatype through the usertype field of the CS_DATAFMT structure.
An Open Server datatype without an associated user-defined datatype is transformed to an ODBC datatype.
The client application can obtain the actual target DBMS datatype for a particular column through the sp_columns CSPs.