1）如果最近更改了SQL Server数据库恢复模型，则应手动发出新的完整备份以恢复数据库备份链。完成此操作后，将来的差异备份应该会成功运行。

1) If the SQL Server database recovery model has recently changed, you should manually issue a new full backup in order to reinstate the database backup chain. Once this is done, future differential backups should run successfully.