Unfortuanately, this is expected behavior in FileMaker. Whenever you get disconnected from the server, any uncommitted records will be lost. This can especially be problematic if you have entered a lot of data into a portal since the new portal records will remain uncommitted until you do an action to commit the records. When you create a record in FileMaker it isn't saved until you do some action to commit the record. This is why you can Revert a record before it is committed. Here is what is happening with the serial number. Let's say the last serial number is 399. If you have the Generate on Creation option, 400 will be inserted into the serial number field for the next new record. If you Revert the record before commiting the record the record will be removed. If you create another record it will get a serial number of 401 eventhough 400 was not used. If you would have had the Generate on commit option checked the serial number would have been set at 400 instead of 401.