在 ALTER DATABASE SET WITNESS 命令执行期间，所有三个服务器实例未保持互连。当前没有与数据库关联的见证服务器。请验证状态并在必要时重复命令。

All three server instances did not remain interconnected for the duration of the ALTER DATABASE SET WITNESS command. There may be no witness associated with the database. Verify the status and when necessary repeat the command.