A backup of the specified Microsoft SQL Server source database is not available. In this situation, Microsoft SQL Server might truncate the online transaction log, even if you have not run the BACKUP LOG command to create a backup of the transaction log. If the online transaction log is truncated, change data might be lost.
Use the BACKUP DATABASE command to perform a full backup of the database. Microsoft SQL Server then does not truncate the online transaction log unless you issue the BACKUP LOG command.