By default, the Upsizing Wizard creates new columns with the data type of timestamp in SQL Server tables generated from Microsoft Access tables which contain floating-point (single or double), memo, or OLE fields.
A timestamp field contains a unique value, generated by SQL Server, which is updated whenever the record is updated. Microsoft Access uses the value in timestamp fields to see if a record has been changed before updating it.
A timestamp field provides the best performance and reliability. In the absence of a timestamp field, the Microsoft Access Jet engine must check all the fields in the record to determine if the record has changed, which slows performance.
Microsoft Access does not check to determine if text or image fields have changed because these fields could be many megabytes in size and the comparison could be too network intensive and time consuming. Therefore, if only a text or image field has changed and there is no timestamp field, the Microsoft Access Jet engine will overwrite the change. Also, the value of a floating-point field may appear to have changed when it hasn't, so Microsoft Access may determine that the record has been changed when it has not.