Difference between Synchronous and Asynchronous in the context of BDC

Synchronization: means it will update record by recod, wait for first record update.

Asynchronous: means will update all records don't wait for next recod. If any record fails syncronus it will stop but in asynchronous it will continue.

In context of BDC: Synchronous means unless and until current records is updated successfully it will not try to update another record, or if the current records fails to update then remaining records will not be updated until we correct the failing data, where as in Asynchronous if current records fails no matter it will be skipped and start updating the next record.