2021年1月23日星期六

关于SQL Server 镜像数据库快照的创建及使用

从SQL Server 2005 SP 起,SQL 开始支持数据库镜像。它的设计目的是试图为SQL Server 提供一个具有实时性数据同步的灾难恢复技术,即能够提供数据冗余备份,切换起来比较方便。每个主体数据库只能有一个镜像数据库。镜像数据库作为主体数据库的一个副本,在主体数据库发生故障、不可访问时能够迅速恢复数据库访问,提供故障恢复功能。镜像数据库一直处于"恢复"状态,因此不能被直接访问。

一.什么是数据库快照

为了提高资源的使用率,想让镜像数据库可以承担部分读,可以借助数据库快照技术。

数据库快照是 SQL Server 数据库(源数据库)的只读静态视图。数据库快照在事务上与创建快照时刻的源数据库一致。一个源数据库可以有多个数据库快照,并且可以作为数据库驻留在一个SQL Server实例中。数据库快照是一个只读的状态,这也就决定了快照的使用场景,那就是用于报表。也可以通过快照快速恢复部分误操作数据。

快照创建时,SQL Server会在实例中创建一个空文件的快照数据库,如果在快照数据库上查询数据,就会被重定向到源数据库中,所以返回的数据都是源数据库的数据。如果在创建数据库快照后,源数据库的原始数据发生了变更,则会把变更前的数据Copy一份写入到对应的数据库快照空白文件中,这时候数据库快照就有了数据,也不再全是空白页了,此时再查询SQL Server数据库快照,查询到的是数据库快照中的数据库(也就是原始数据的副本)。快照文件的大小随着对源数据库的更改而增大。 注意:数据库快照在数据页级运行。在第一次修改源数据库页之前,先将原始页从源数据库复制到快照。快照将存储原始页,保留它们在创建快照时的数据记录。 对要进行第一次修改的每一页重复此过程。

二.实现创建数据库快照的SP

1.时间格式函数FormatDate

在前面的学习分析中,我们知道一个源数据库可以有多个快照,所以,为了区别同时存在的多快照,我们对快照的命名基于了时间(即包含了时间元素),例如:

SS_DBName_19022311(2019年2月23号11点产生的快照);SS_DBName_19022312(2019年2月23号12点产生的快照);SS_DBName_19022313(2019年2月23号13点产生的快照)。所以,先编写创建时间格式函数FormatDate。此外,快照以SS_开头是为了标示此对象为数据库快照,与其他数据库对象区别开,便于运维管理,SS为Snapshots的缩写。

USE [master]GO/****** Object: UserDefinedFunction [dbo].[FormatDate] Script Date: 2019/1/22 17:37:53 ******/SET ANSI_NULLS ONGOSET QUOTED_IDENTIFIER ONGOCreate FUNCTION [dbo].[FormatDate](@date as datetime,@formatstring as varchar(100))RETURNS varchar(100) AS BEGIN  declare @datestring as varchar(100) set @datestring=@formatstring --year set @datestring=replace(@datestring, 'yyyy', cast(year(@date) as char(4))) set @datestring=replace(@datestring, 'yy', right(cast(year(@date) as char(4)),2)) --millisecond set @datestring=replace(@datestring, 'ms', replicate('0',3-len(cast(datepart(ms,@date) as varchar(3)))) + cast(datepart(ms, @date) as varchar(3))) --month set @datestring=replace(@datestring, 'mm', replicate('0',2-len(cast(month(@date) as varchar(2)))) + cast(month(@date) as varchar(2))) set @datestring=replace(@datestring, 'm', cast(month(@date) as varchar(2))) --day set @datestring=replace(@datestring, 'dd', replicate('0',2-len(cast(day(@date) as varchar(2)))) + cast(day(@date) as varchar(2))) set @datestring=replace(@datestring, 'd', cast(day(@date) as varchar(2))) --hour set @datestring=replace(@datestring, 'hh', replicate('0',2-len(cast(datepart(hh,@date) as varchar(2)))) + cast(datepart(hh, @date) as varchar(2))) set @datestring=replace(@datestring, 'h', cast(datepart(hh, @date) as varchar(2)))  --minute set @datestring=replace(@datestring, 'nn', replicate('0',2-len(cast(datepart(n,@date) as varchar(2)))) + cast(datepart(n, @date) as varchar(2))) set @datestring=replace(@datestring, 'n', cast(datepart(n, @date) as varchar(2))) --second set @datestring=replace(@datestring, 'ss', replicate('0',2-len(cast(datepart(ss,@date) as varchar(2)))) + cast(datepart(ss, @date) as varchar(2))) set @datestring=replace(@datestring, 's', cast(datepart(ss, @date) as varchar(2))) return @datestringENDGO

2.创建快照的SP

(1)首先明确那些DB需要创建快照。这里是从MirrorDB 中筛选的,并且,IN()可以定义多个数据库。定义部分如下:

(2)明确数据库快照保留的个数

         

 (3)具体的创建脚本

USE [master]GO/****** Object: StoredProcedure [dbo].[CreateSnapshotDB_By1H] Script Date: 2019/1/22 17:39:07 ******/SET ANSI_NULLS ONGOSET QUOTED_IDENTIFIER ONGO----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------*Program*: <Create Snapshot DB for Mirror DB>--*Programer*:<Carson.Xu>--*Date*:<2019/01/21>--*Unify*:<ALL> --*Description*:<Create Snapshot DB for Mirror DB>--########## Parameter Description Begin ##########--########## Parameter Description End # ########## --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------CREATE PROCEDURE [dbo].[CreateSnapshotDB_By1H] AS set nocount ondeclare @sSql nvarchar(2000) declare @sMsg varchar(4000) declare @TransDT varchar(10)declare @SS_DBName varchar(40)='' declare @DBLogic_FileName varchar(40)='' declare @SnapshotDBType varchar(40)='' declare @SS_NewDBName varchar(40)='' declare @SS_NewDB_FileName varchar(50)='' Declare @RestorePath varchar(200) create table #DBLogic (Name nvarchar(200) )create table #OldSS_DB (Name nvarchar(200) )set @sMsg=''set @RestorePath='D:\SnapShot' select @TransDT=dbo.FormatDate(GETDATE(),'YYYYMMDDHH')select DB_NAME(database_id) as DBName,database_id, mirroring_partner_name Into #MirrorDB from sys.database_mirroring where mirroring_guid is not null and DB_NAME(database_id) in('Your_DBName') While exists(Select top 1 * from #MirrorDB )begin --SS_JON/QFMS_MMDDHH select top 1 @SnapshotDBType=DBName from #MirrorDB  set @SS_NewDBName='SS_'+@SnapshotDBType+'_'+Right(@TransDT,6) --print @SS_NewDBName  IF exists(select Name from sys.databases where name = @SS_NewDBName ) BEGIN   BEGIN   set @sSql='drop DATABASE '+ @SS_NewDBName   exec sp_executesql @sSql   END END  Insert into #DBLogic select Name from sys.master_files where DB_NAME(database_id)=@SnapshotDBType and type=0 if not exists(select Name from sys.databases where name = @SS_NewDBName )  begin    set @sSql=' CREATE DATABASE '+@SS_NewDBName +' ON '   select @sSql= @sSql+ '( NAME ='+Name +', FILENAME = '''+@RestorePath+ '\'+@SnapshotDBType+         '\SS_'+Name+'_'+ left(@TransDT,10)+'.SS''),' from #DBLogic    if right(@sSql,1)=','    begin     set @sSql=SUBSTRING( @sSql,1,LEN(@sSql)-1 )    end   set @sSql=@sSql+' AS SNAPSHOT OF ['+ @SnapshotDBType +']'      print @sSql   exec sp_executesql @sSql  end  else  begin   print 'Drop SnapShot DB('+@SS_NewDBName+' fail, it can not create it again! transDT:' +@TransDT  end  Declare @TempSS_DB nvarchar(200)  ----删除历史快照 Insert Into #OldSS_DB select Name from sys.databases where name like 'SS_'+@SnapshotDBType+'%' and create_date < dateadd(hour,-3, GETDATE()) while exists(Select * from #OldSS_DB) begin  select top 1 @TempSS_DB=Name from #OldSS_DB  set @sSql='drop DATABASE '+ @TempSS_DB   exec sp_executesql @sSql  delete from #OldSS_DB where Name=@TempSS_DB end  delete from #DBLogic delete from #MirrorDB where DBName =@SnapshotDBTypeend GO

 3.创建便于访问的快照

上面的SP是创建了以时间命名的DB快照,创建时间不同,快照的名字就会不同。但是,如果DB名字不同,程序应用调用起来就非常不方便。所以我们还希望可以创建一个不带时间的数据库快照,每次创建数据的快照名字是一样的。这样前端应用程序访问数据库就不再需要修改数据库的连接配置了。

下面这个SP就是为了解决这个上面这个应用场景。代码将数据库的快照命名为SS_DBName。为了包含融合前面SP的功能,这份SP还直接调用了存储过程CreateSnapshotDB_By1H----EXEC [dbo].[CreateSnapshotDB_By1H]

USE [master]GO/****** Object: StoredProcedure [dbo].[CreateSnapshotDB] Script Date: 2019/1/22 17:40:57 ******/SET ANSI_NULLS ONGOSET QUOTED_IDENTIFIER ONGO----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------*Program*: <Create Snapshot DB for Mirror DB>--*Programer*:<Carson Xu>--*Date*:<2019/01/21>--*Unify*:<ALL> --*Description*:<Create Snapshot DB for Mirror DB>--########## Parameter Description Begin ##########--########## Parameter Description End # ########## --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Create PROCEDURE [dbo].[CreateSnapshotDB] AS BEGIN set nocount ondeclare @sSql nvarchar(2000) declare @sMsg varchar(4000) declare @SS_DBName varchar(40)=''declare @TransDT char(10) declare @DBLogic_FileName varchar(40)='' declare @SnapshotDBType varchar(40)='' declare @SS_NewDBName varchar(40)='' declare @SS_NewDB_FileName varchar(50)='' Declare @RestorePath varchar(200) create table #DBLogic (Name nvarchar(200) )create table #OldSS_DB (Name nvarchar(200) )set @sMsg=''set @RestorePath='D:\SnapShot' select @TransDT=dbo.FormatDate(GETDATE(),'YYYYMMDDHH')Set @sSql='"MD '+@RestorePathEXEC master..xp_cmdshell @sSql ,no_outputselect DB_NAME(database_id) as DBName,database_id, mirroring_partner_name Into #MirrorDB from sys.database_mirroring where mirroring_guid is not null and DB_NAME(database_id) in('Your_DBName') While exists(Select top 1 * from #MirrorDB )begin --SS_SMT/QSMS_MMDDHH select top 1 @SnapshotDBType=DBName from #MirrorDB   Set @sSql='"MD '+@RestorePath +'\'+@SnapshotDBType EXEC master..xp_cmdshell @sSql ,no_output  set @SS_NewDBName='SS_'+@SnapshotDBType --print @SS_NewDBName  IF exists(select Name from sys.databases where name = @SS_NewDBName ) BEGIN   BEGIN    set @sSql='drop DATABASE '+ @SS_NewDBName   exec sp_executesql @sSql   END END  Insert into #DBLogic select Name from sys.master_files where DB_NAME(database_id)=@SnapshotDBType and type=0 if not exists(select Name from sys.databases where name = @SS_NewDBName )  begin    set @sSql=' CREATE DATABASE '+@SS_NewDBName +' ON '   select @sSql= @sSql+ '( NAME ='+Name +', FILENAME = '''+@RestorePath+ '\'+@SnapshotDBType+         '\SS_'+Name+'.SS''),' from #DBLogic    if right(@sSql,1)=','    begin     set @sSql=SUBSTRING( @sSql,1,LEN(@sSql)-1 )    end   set @sSql=@sSql+' AS SNAPSHOT OF ['+ @SnapshotDBType +']'      print @sSql   exec sp_executesql @sSql  end  else  begin   print 'Drop SnapShot DB('+@SS_NewDBName+' fail, it can not create it again! transDT:' +@TransDT  end  delete from #DBLogic delete from #MirrorDB where DBName =@SnapshotDBTypeend EXEC [dbo].[CreateSnapshotDB_By1H] END GO

 以上代码为创建镜像DB快照使用到的函数和存储过程。在调试部署OK后,就可以设置Job了,让其每小时自动执行一次。Job的设置就不再赘言了,核心代码就是:

exec CreateSnapshotDB

三.同步主体、镜像数据库间的账号

系统数据库不能被镜像,用户名密码自然也不能被同步到Mirror服务器上。快照的用户权限继承于源库,但是MIrror 实例上并没有相应的账号信息。所以,需要先到主体数据库(Principal Database)上导出用户的账号信息(可以指定某个账号),然后将打印出的SQL语句Copy至Mirror实例上执行一下就可以了。

主要使用的SP为sp_help_revlogin,但是这个SP会调用到sp_hexadecimal。

1.先创建基础SP:sp_hexadecimal

USE [master]GO/****** Object: StoredProcedure [dbo].[sp_hexadecimal] Script Date: 2019/1/22 17:48:06 ******/SET ANSI_NULLS ONGOSET QUOTED_IDENTIFIER ONGO CREATE PROCEDURE [dbo].[sp_hexadecimal] @binvalue varbinary(256), @hexvalue varchar (514) OUTPUT AS DECLARE @charvalue varchar (514) DECLARE @i int DECLARE @length int DECLARE @hexstring char(16) SELECT @charvalue = '0x' SELECT @i = 1 SELECT @length = DATALENGTH (@binvalue) SELECT @hexstring = '0123456789ABCDEF' WHILE (@i <= @length) BEGIN DECLARE @tempint int DECLARE @firstint int DECLARE @secondint int SELECT @tempint = CONVERT(int, SUBSTRING(@binvalue,@i,1)) SELECT @firstint = FLOOR(@tempint/16) SELECT @secondint = @tempint - (@firstint*16) SELECT @charvalue = @charvalue + SUBSTRING(@hexstring, @firstint+1, 1) + SUBSTRING(@hexstring, @secondint+1, 1) SELECT @i = @i + 1 END SELECT @hexvalue = @charvalue GO

 2.创建导出用户信息的SP:sp_help_revlogin

USE [master]GO/****** Object: StoredProcedure [dbo].[sp_help_revlogin] Script Date: 2019/1/22 17:52:39 ******/SET ANSI_NULLS ONGOSET QUOTED_IDENTIFIER ONGO CREATE PROCEDURE [dbo].[sp_help_revlogin] @login_name sysname = NULL AS DECLARE @name sysname DECLARE @type varchar (1) DECLARE @hasaccess int DECLARE @denylogin int DECLARE @is_disabled int DECLARE @PWD_varbinary varbinary (256) DECLARE @PWD_string varchar (514) DECLARE @SID_varbinary varbinary (85) DECLARE @SID_string varchar (514) DECLARE @tmpstr varchar (1024) DECLARE @is_policy_checked varchar (3) DECLARE @is_expiration_checked varchar (3) DECLARE @defaultdb sysname IF (@login_name IS NULL) DECLARE login_curs CURSOR FOR SELECT p.sid, p.name, p.type, p.is_disabled, p.default_database_name, l.hasaccess, l.denylogin FROM sys.server_principals p LEFT JOIN sys.syslogins l ON ( l.name = p.name ) WHERE p.type IN ( 'S', 'G', 'U' ) AND p.name <> 'sa' ELSE DECLARE login_curs CURSOR FOR SELECT p.sid, p.name, p.type, p.is_disabled, p.default_database_name, l.hasaccess, l.denylogin FROM sys.server_principals p LEFT JOIN sys.syslogins l ON ( l.name = p.name ) WHERE p.type IN ( 'S', 'G', 'U' ) AND p.name = @login_name OPEN login_curs FETCH NEXT FROM login_curs INTO @SID_varbinary, @name, @type, @is_disabled, @defaultdb, @hasaccess, @denylogin IF (@@fetch_status = -1) BEGIN PRINT 'No login(s) found.' CLOSE login_curs DEALLOCATE login_curs RETURN -1 END SET @tmpstr = '/* sp_help_revlogin script ' PRINT @tmpstr SET @tmpstr = '** Generated ' + CONVERT (varchar, GETDATE()) + ' on ' + @@SERVERNAME + ' */' PRINT @tmpstr PRINT '' WHILE (@@fetch_status <> -1) BEGIN IF (@@fetch_status <> -2) BEGIN PRINT '' SET @tmpstr = '-- Login: ' + @name PRINT @tmpstr IF (@type IN ( 'G', 'U')) BEGIN -- NT authenticated account/group SET @tmpstr = 'CREATE LOGIN ' + QUOTENAME( @name ) + ' FROM WINDOWS WITH DEFAULT_DATABASE = [' + @defaultdb + ']' END ELSE BEGIN -- SQL Server authentication -- obtain password and sid SET @PWD_varbinary = CAST( LOGINPROPERTY( @name, 'PasswordHash' ) AS varbinary (256) ) EXEC sp_hexadecimal @PWD_varbinary, @PWD_string OUT EXEC sp_hexadecimal @SID_varbinary,@SID_string OUT -- obtain password policy state SELECT @is_policy_checked = CASE is_policy_checked WHEN 1 THEN 'ON' WHEN 0 THEN 'OFF' ELSE NULL END FROM sys.sql_logins WHERE name = @name SELECT @is_expiration_checked = CASE is_expiration_checked WHEN 1 THEN 'ON' WHEN 0 THEN 'OFF' ELSE NULL END FROM sys.sql_logins WHERE name = @name SET @tmpstr = 'CREATE LOGIN ' + QUOTENAME( @name ) + ' WITH PASSWORD = ' + @PWD_string + ' HASHED, SID = ' + @SID_string + ', DEFAULT_DATABASE = [' + @defaultdb + ']' IF ( @is_policy_checked IS NOT NULL ) BEGIN SET @tmpstr = @tmpstr + ', CHECK_POLICY = ' + @is_policy_checked END IF ( @is_expiration_checked IS NOT NULL ) BEGIN SET @tmpstr = @tmpstr + ', CHECK_EXPIRATION = ' + @is_expiration_checked END END IF (@denylogin = 1) BEGIN -- login is denied access SET @tmpstr = @tmpstr + '; DENY CONNECT SQL TO ' + QUOTENAME( @name ) END ELSE IF (@hasaccess = 0) BEGIN -- login exists but does not have access SET @tmpstr = @tmpstr + '; REVOKE CONNECT SQL TO ' + QUOTENAME( @name ) END IF (@is_disabled = 1) BEGIN -- login is disabled SET @tmpstr = @tmpstr + '; ALTER LOGIN ' + QUOTENAME( @name ) + ' DISABLE' END PRINT @tmpstr END FETCH NEXT FROM login_curs INTO @SID_varbinary, @name, @type, @is_disabled, @defaultdb, @hasaccess, @denylogin END CLOSE login_curs DEALLOCATE login_curs RETURN 0 GO

 

四.快照原理请参阅以下分享

1.https://docs.microsoft.com/zh-cn/sql/relational-databases/databases/database-snapshots-sql-server?view=sql-server-ver15

2.https://www.zhihu.com/question/305701792









原文转载:http://www.shaoqun.com/a/512657.html

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从SQLServer2005SP起,SQL开始支持数据库镜像。它的设计目的是试图为SQLServer提供一个具有实时性数据同步的灾难恢复技术,即能够提供数据冗余备份,切换起来比较方便。每个主体数据库只能有一个镜像数据库。镜像数据库作为主体数据库的一个副本,在主体数据库发生故障、不可访问时能够迅速恢复数据库访问,提供故障恢复功能。镜像数据库一直处于"恢复"状态,因此不能被直接访问。一.什么是数据库快
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