PRB: 32K Limit on Direct Parameters for 16-bit Drivers (126614)

SYMPTOMS

If you use SQLBindParameter to directly pass more than 32K of data to a SQL statement against 16-bit desktop database drivers, you will get the following error message:

SQL_ERROR: Memory allocation failure.

The following is a piece of the code to duplicate the error:

   //data source is an access table objtab with only one OLE field.
   //16-bit Access driver 2.00.2317 is used

   SQLPrepare(hstmt, "insert into objtab(?)", SQL_NTS);
   BigObj = AllocateMemory(sizeof(UCHAR) * 32800);
   cbBigObj = 32800;
   SQLBindParameter(
      hstmt, 1, SQL_PARAM_INPUT, SQL_C_BINARY, SQL_C_LONGVARCHAR,
      32800, 0, BigObj, 32800, &cbBigObj);
   //Prepare the BigObj
   SQLExecute(hstmt);

Returns:

SQL Error State:S1001; Native Error Code: 34;
ODBC Error:[Microsoft][ODBC Microsoft Access 2.0 Driver]memory allocation failure.

NOTE: If cbBigObj is changed to 32750 (with corresponding changes in SQLBindParameter), SQLExecute will succeed.

CAUSE

The internal buffer for direct parameters passed to the 16-bit desktop database drivers is limited to 32K.

NOTE: You will actually have a little less than 32K of total parameters, because some space is taken up by a length byte in the internal buffer.

RESOLUTION

Use 32-bit drivers if you can.
Use SQLPutData to send it in installments. Using direct parameters is not recommended to pass in large data. Instead, you can use data-at-execution with SQLPutData.
Use SQLExtendedFetch and SQLSetPos...SQL_ADD, which is faster. Because all of the parameters are not copied into a separate buffer before being passed into the internal buffer, you save a memcopy.