通过SMSS工具执行一个备份清理任务，备份成功，删除却老是失败
在安装目录找到log文件 ,日志如下，单独执行命令又可以删除，后来找到原因是backup目录下面存放了不是备份计划的Bak文件，将手动删除后，自动清理任务恢复正常。
Maintenance Cleanup on Local server connection
Cleanup Database Backup files
Age: Older than 1 Weeks
Task start: 2019-04-16T19:03:08.
Task end: 2019-04-16T19:03:08.
Failed:(-1073548784) Executing the query "EXECUTE master.dbo.xp_delete_file 0,N'',N'',N'2019..." failed with the following error: "Error executing extended stored procedure: Invalid Parameter". Possible failure reasons: Problems with the query, "ResultSet"
property not set correctly, parameters not set correctly, or connection not established correctly.