SQL Server数据库日志清除的两个方法

以下为引用的内容：

set nocount on
declare @logicalfilename sysname,
        @maxminutes int,
        @newsize int

use     tablename            
-- 要操作的数据库名
select  @logicalfilename='tablename_log', 
-- 日志文件名
@maxminutes=10,              
-- limit on time allowed to wrap log.
        @newsize=1                 
-- 你想设定的日志文件的大小(m)

-- setup / initialize
declare @originalsize int
select @originalsize=size
  from sysfiles
  where name=@logicalfilename
select 'original size of ' + db_name() + ' log is ' +
        convert(varchar(30),@originalsize) + ' 8k pages or ' +
        convert(varchar(30),(@originalsize*8/1024)) + 'mb'
  from sysfiles
  where name=@logicalfilename
create table dummytrans
  (dummycolumn char (8000) not null)

declare @counter   int,
        @starttime datetime,
        @trunclog  varchar(255)
select  @starttime=getdate(),
        @trunclog='backup log '
 + db_name() + ' with truncate_only'

dbcc shrinkfile (@logicalfilename, @newsize)
exec (@trunclog)
-- wrap the log if necessary.
while     @maxminutes > datediff
(mi, @starttime, getdate()) -- time has not expired
      and @originalsize=
(select size from sysfiles where name=@logicalfilename) 
      and (@originalsize * 8 /1024) > @newsize 
  begin -- outer loop.
    select @counter=0
    while  ((@counter < @originalsize / 16) and (@counter < 50000))
      begin -- update
        insert dummytrans values ('fill log') 
        delete dummytrans
        select @counter=@counter + 1
      end  
    exec (@trunclog) 
  end  
select 'final size of ' + db_name() + ' log is ' +
        convert(varchar(30),size) + ' 8k pages or ' +
        convert(varchar(30),(size*8/1024)) + 'mb'
  from sysfiles
  where name=@logicalfilename
drop table dummytrans
set nocount off