If a password was provided when the media set was formatted , that password must be supplied to create a backup set on that media set 如果格式化媒体集时提供了密码，则在该媒体集上创建备份集时必须提供密码。
If backup writes the media header , backup will assign the media set password to the value specified in the mediapassword option 如果backup写入媒体标头， backup将给mediapassword选项中指定的值分配媒体集密码。
When a password has been defined on a media set or backup set , you must specify the correct password or passwords in the restore statement 如果已经在媒体集或备份集上定义了密码，则必须在restore语句中指定正确的密码。
The following example shows how to create a full database backup by using with format to overwrite any existing backups and create a new media set 在简单恢复模式下，每次备份后，数据库都有可能在出现严重故障时丢失工作。
Typically , backups are unmirrored , and backup statements simply include a to clause . however , a total of four mirrors is possible per media set 对于镜像媒体集，每个mirror to子句列出的设备数量（以及类型）都必须与to子句列出的相同。
To back up to a mirrored media set , specify the to clause to specify the first mirror , and specify a mirror to clause for each additional mirror 以下示例将用于这些设备上的第一个备份，因此使用with format子句。 （若要将备份追加到这些设备，请省略with format子句。
