Synchronization warnings are displayed at the Summary Page of the Data Synchronization wizard. These warnings are the same as column level Mapping Warnings. But mapping warnings appear regardless of real data differences, they are generated if there are column data type differences, which may cause errors or data loss in the tables to compare. Synchronization warnings appear only if there are data to be updated or inserted to the target table.
If you encountered synchronization warnings, than synchronization may fail or data loss may occur because of truncation or rounding. If the warning has a red circle icon with a cross inside, then the error will certainly occur when executing synchronization script. To avoid this error, exclude this table or corresponding records from synchronization by clearing the corresponding check boxes in the Data Comparison document.