删除备份集,该怎么处理

--删除过期的备份文件,每天两次
declare @str varchar(100),@dir varchar(100),@fileName varchar(30)
set @dir='del D:\DBtext\jgj\DBABak\'
set @filename=left(replace(replace(replace(convert(varchar,getdate()-15,20),'-',''),' ',''),':',''),8)
set @str=@dir+'fullbak'+@filename+'*.bak'
exec xp_cmdshell @str
set @filename=left(replace(replace(replace(convert(varchar,getdate()-8,20),'-',''),' ',''),':',''),8)
set @str=@dir+'diffbak'+@filename+'*.diff'
exec xp_cmdshell @str
set @filename=left(replace(replace(replace(convert(varchar,getdate()-8,20),'-',''),' ',''),':',''),8)
set @str=@dir+'logbak'+@filename+'*.trn'
exec xp_cmdshell @str