Docs: SpeedGen Desktop: The ReadAhead Parameter

• Set to 0 to disable. In many cases this will still be slower than a value of 1.
• ReadAheads uses GetRows. The ReadAhead property performs its magic by calling the GetRows method of the ADO or DAO RecordSet. Therefore you never need to worry about implementing a call to GetRows yourself. In fact, you will never be able to achieve the memory conservation that SpeedGen gets because when it uses ReadAhead it uses only the Fields required for the current row on the spreadsheet.
• Experiment for Best Performance. If you have a large number of Rows or Fields then you should really experiment with this value. Try small, medium and large values (0, 10, 50, 100) to see what works best.
• If ReadAhead is larger than the number of rows in the RecordSet, then all Rows will be read into memory.

ADO Notes

• Only Required Fields are Loaded. Only the fields that are used in the Excel rows currently being written are loaded into memory. So you don't have to worry about binary or other fields accidentally being loaded into memory.

DAO Notes

• All fields in the row are read into memory. This is a DAO limitation. ADO does not have this limitation. If you have binary data in one of the fields, but are not writing that field to the Spreadsheet then you should either replace your RecordSet with a Query of only the fields you need or disable ReadAhead ( ReadAhead = 0 ).