SQL Server 2005 Backing Up & Restoring Databases

Transcription

1 Institute of Informatics, Silesian University of Technology, Gliwice, Poland SQL Server 2005 Backing Up & Restoring Databases Dariusz Mrozek, PhD Course name: SQL Server DBMS

2 Part 1: Backing Up Overview Preventing Data Loss Setting and Changing a Database Recovery Model SQL Server Backup When to Back Up Databases Performing Backups Types of Backup Methods Planning a Backup Strategy 2

3 Preventing Data Loss Have a Backup Strategy To minimize data loss To recover lost data To restore data with minimal cost to production time Back Up Regularly 3

4 Ways we can lose data You can lose data as a result of hardware or software failures or: Accidental or malicious use of the DELETE statement. Accidental or malicious use of the UPDATE statement for example, not using a WHERE clause with the UPDATE statement (all rows are updated rather than a single row in a particular table). Destructive viruses. Natural disasters, such as fire, flood, and earthquakes. Theft. How much am I willing to pay, and how much loss is acceptable to me? 4

5 Back Up Regularly You might back up your database frequently if your system is in an online transaction processing (OLTP) environment. You might back up your database less frequently if your system has little activity or is used primarily for decision support. You should schedule backups when SQL Server is not in the process of being heavily updated. After you determine your backup strategy, you can automate the process by using the SQL Server Agent. 5

6 Setting and Changing a Database Recovery Model Setting a Database Recovery Model Full Recovery model uses copies of the database and all log information to restore the database recover all data except transactions actually in process at the time of the failure Bulk_Logged Recovery model similar to Full uses less log space for some operations can restore all data Simple Recovery model for small databases or databases where data changes infrequently recovery is limited to restoring the database to the point when the last backup was made takes less storage space for logs and is the simplest model to implement Changing a Database Recovery Model ALTER DATABASE AdventureWorks SET RECOVERY BULK_LOGGED 6

7 SQL Server Backup Allows Backups to Occur While Users Continue to Work with the Database Backs Up Original Files and Records Their Locations Captures Database Activities That Occur During the Backup Process in the Backup Issues a checkpoint and records the LSN Writes all pages to the backup media Writes all transaction log records written during the backup process 7

8 Performing and Storing Backups Who Performs Backups Members of the sysadmin fixed server role Members of the db_owner and db_backupoperator fixed database roles Where to Store Backups Hard disk file Tape Network resource 8

9 When to Back Up Databases Backing Up System Databases Backing Up User Databases Activities That Are Restricted During Backup 9

10 Backing Up System Databases After Modifying the master Database Using the CREATE DATABASE, ALTER DATABASE, or DROP DATABASE statement Executing certain system stored procedures, like: sp_addserver, sp_dropserver, sp_addlinkedserver, sp_addmessage, After Modifying the msdb Database After Modifying the model Database 10

11 Backing Up User Databases After Creating Databases After Creating Indexes After Clearing the Transaction Log After Performing Nonlogged Operations BACKUP LOG WITH TRUNCATE_ONLY or NO_LOG statement WRITETEXT or UPDATETEXT statement SELECT...INTO statement 11

12 Activities That Are Restricted During Backup Creating or Modifying Databases Performing Autogrow Operations Creating Indexes Performing Nonlogged Operations Shrinking a Database 12

13 Performing Backups Creating Backup Devices Creating Backup Files Without Permanent Devices Using Multiple Backup Files to Store Backups Using the BACKUP Statement Backing Up to a Tape Device 13

14 Creating Backup Devices Why to Create Permanent Backup Devices To reuse the backup files for future backups To automate the task of backing up Using the sp_addumpdevice System Stored Procedure Specify the logical name Logical and physical names are stored in the sys.backup_devices system table USE master GO EXEC sp_addumpdevice 'disk', 'AWBackupDevice', 'C:\Backup\AWbackup.bak' GO 14

15 Creating Backup Devices USE master; GO sp_addumpdevice = ] 'device_type', = ] 'logical_name', = ] 'physical_name USE master; GO EXEC sp_addumpdevice 'disk', 'networkdevice', '\\<servername>\<sharename>\<path>\<filename>.bak'; USE master; GO EXEC sp_addumpdevice 'tape', 'tapedump1', '\\.\tape0'; 15

16 Creating Backup Devices 16

17 Backuping Database BACKUP DATABASE { } TO < backup_device > [,...n ] [ [ MIRROR TO < backup_device > [,...n ] ] [...next-mirror ] ] [ WITH [ BLOCKSIZE = { } ] [ [, ] { CHECKSUM NO_CHECKSUM } ] [ [, ] { STOP_ON_ERROR CONTINUE_AFTER_ERROR } ] [ [, ] DESCRIPTION = { } ] [ [, ] DIFFERENTIAL ] [ [, ] EXPIREDATE = { } RETAINDAYS = { } ] [ [, ] PASSWORD = { } ] [ [, ] { FORMAT NOFORMAT } ] [ [, ] { INIT NOINIT } ] [ [, ] { NOSKIP SKIP } ] [ [, ] MEDIADESCRIPTION = { } ] [ [, ] MEDIANAME = { } ] [ [, ] MEDIAPASSWORD = { } ] [ [, ] NAME = { } ] [ [, ] { NOREWIND REWIND } ] [ [, ] { NOUNLOAD UNLOAD } ] [ [, ] RESTART ] [ [, ] STATS [ = percentage ] ] [ [, ] COPY_ONLY ] ] 17

18 Backuping Database USE master GO BACKUP DATABASE AdventureWorks TO AWBackupDev GO USE master GO RESTORE HEADERONLY FROM AWBackupDev GO 18

19 Backuping Database 19

20 Creating Backup Files Without Permanent Devices Why to Create Backup Files Without Permanent Devices To perform a one-time-only backup To test the backup operation that you plan to automate Using the BACKUP DATABASE Statement Specify a media type (disk, tape) Specify the complete path and file name USE master BACKUP DATABASE AdventureWorks TO DISK = 'C:\AdventureWorks.bak' 20

21 Storing Backups on Multiple Backup Files A backup set is a result of a single backup operation on single or multiple files. A media set is an ordered collection of backup media, tapes or disk files, to which one or more backup operations have written using a fixed type and number of backup devices. Backuping to multiple tapes or disk controllers decreases the total time that it takes to back up a database. BACKUP DATABASE TO <backup_device> [,...n] [WITH [MEDIANAME = ] 21

22 Using Multiple Backup Files to Store Backups Database A Database B Media Set Backup Set File 1 File 2 File 3 BackupA1 BackupA2 BackupA3 BackupA1 BackupA2 BackupA3 BackupA1 BackupB1 BackupA2 BackupA3 BackupB1 BackupB1 BackupB1 22

23 Storing Backups on Multiple Backup Files All devices that are used in a single backup operation must be of the same media type (disk or tape). You cannot mix disk and tape devices for a single backup media set. You can use a combination of permanent and temporary files when you create a backup set. If you define a file as a member of a backup set, you must always use the files together. You cannot use only one member of the backup set for a backup operation unless you reformat the files. If you reformat one member of a backup set, the data that is contained in the other members of the backup set is invalid and unusable. BACKUP DATABASE AdventureWorks TO DISK='C:\AdventureWorks1a.bak', DISK='C:\AdventureWorks2a.bak', DISK='C:\AdventureWorks3a.bak' MIRROR TO DISK='C:\AdventureWorks1b.bak', DISK='C:\AdventureWorks2b.bak', DISK='C:\AdventureWorks3b.bak' WITH FORMAT, STATS=10 23

24 Using the BACKUP Statement Specifying the INIT or NOINIT Option NOINIT option appends to a backup file INIT option overwrites a backup file Using the FORMAT Option Overwrites the contents of a backup file Splits up a striped backup set USE master GO BACKUP DATABASE AdventureWorks TO DISK='C:\AdventureWorks1.bak WITH INIT, STATS=10 24

25 Backing Up to a Tape Device Requires Tape to Be Attached Locally to SQL Server Records Backup Information on Tape Label Database name Time Date Type of backup Stores SQL Server and Non-SQL Server Backups (e.g. Microsoft Windows XP backups) USE master GO BACKUP DATABASE AdventureWorks TO TAPE= \\.\tape0 WITH STATS=10 25

26 Specifying Tape Options Tape option UNLOAD (default) NOUNLOAD BLOCKSIZE FORMAT SKIP NOSKIP (default) RESTART Description Rewinds and unloads the tape Does not rewind and unload the tape Changes the physical block size in bytes Writes a header on files that are used for a backup Ignores ANSI tape labels Reads ANSI tape labels Restarts the backup operation from the point of interruption 26

27 Types of Backup Methods Performing a Full Database Backup Performing a Differential Backup Performing a Transaction Log Backup Performing a Database File or Filegroup Backup 27

28 Performing a Full Database Backup Provides a Baseline Backs Up Original Files, Objects, and Data Backs Up Portions of the Transaction Log Backs up any activity that took place during the backup. Backs up any uncommitted transactions in the transaction log. USE master EXEC sp_addumpdevice 'disk', AWBacDev', 'D:\MyBackupDir\AWBackup.bak' BACKUP DATABASE AdventureWorks TO AWBacDev AdventureWorks D:\ Data Log Backup AWBacDev 28

29 Performing a Differential Backup Use on Frequently Modified Databases Requires a Full Database Backup Backs Up Database Changes Since the Last Full Database Backup Saves Time in Both Backup and Restore Process BACKUP DATABASE AdventureWorks DISK = 'D:\MyData\MyDiffBackup.bak' WITH DIFFERENTIAL 29

30 Performing a Transaction Log Backup Requires a Full Database Backup Backs Up All Database Changes from the Last BACKUP LOG Statement to the End of the Current Transaction Log Truncates the Transaction Log NOTE: You cannot back up transaction logs when using the Simple Recovery model. USE master EXEC sp_addumpdevice 'disk', AWBacDevLog', 'D:\Backup\AWBackupLog.bak' BACKUP LOG AdventureWorks TO AWBacDevLog 30

31 Using the NO_TRUNCATE Option SQL Server: Saves the Entire Transaction Log Even if the Database Is Inaccessible Does Not Purge the Transaction Log of Committed Transactions Allows Data to Be Recovered Up to the Time When the System Failed USE master EXEC sp_addumpdevice 'disk', AWBacDevLog', 'D:\Backup\AWBackupLog.bak' BACKUP LOG AdventureWorks TO AWBacDevLog WITH NO_TRUNCATE 31

32 Clearing the Transaction Log Use the BACKUP Statement to Clear the Transaction Log Using the TRUNCATE_ONLY or NO_LOG Option Cannot recover changes use BACKUP DATABASE shortly Is not recorded USE master GO BACKUP LOG AdventureWorks WITH TRUNCATE_ONLY 32

33 Performing a Database File or Filegroup Backup Use on Very Large Databases Back Up the Database Files Individually Ensure That All Database Files in Filegroup Are Backed Up Back Up Transaction Logs BACKUP DATABASE AdventureWorks FILE = AWorks2 TO AWorksBackup2 GO BACKUP LOG AdventureWorks to AWorksBackLog GO 33

34 Restrictions on Backing Up Database Files or Filegroups Scenario 1 D:\ Table Index Filegroup1 Both files must be backed up as a unit Index 1 Table Filegroup 2 Filegroup 1 Index 2 Filegroup 3 Scenario 2 Filegroups 1, 2, and 3 must be backed up as a unit D:\ 34

35 Planning a Backup Strategy Full Database Backup Strategy Full Database and Transaction Log Backup Strategy Differential Backup Strategy Database File or Filegroup Backup Strategy 35

36 Full Database Backup Strategy Created Database and Performed Full Database Backup Full Database Backup Full Database Backup Data Log Data Log Data Log Sunday Monday Tuesday 36

37 Full Database and Transaction Log Backup Strategy Full Database Backup Full Database Backup Data Log Log Log Log Log Data Log Sunday Monday 37

38 Differential Backup Strategy Full Database Backup Differential Backup Differential Backup Data Log Log Log Log Log Log Log Data Log... Monday Tuesday 38

39 Database File or Filegroup Backup Strategy Full Database Backup Data Data Data Data Log Log Log Log Log Log Log Log Log File 1 File 2 File 3 Monday Tuesday Wednesday Thursday 39

40 Performance Considerations Back Up to Multiple Physical Devices Type of Physical Backup Device Determines Speed if Backup Process Minimize Concurrent Activity on SQL Server 40

41 Recommended Practices Have a Backup Strategy Back Up System Databases After They Have Been Modified Schedule Backup Operations When Database Activity Is Low Create Backup Devices Test Your Backup Strategy 41

42 Backup Review Preventing Data Loss Setting and Changing a Database Recovery Model SQL Server Backup When to Back Up Databases Performing Backups Types of Backup Methods Planning a Backup Strategy 42

43 Part 2: Restoring Overview SQL Server Recovery Process Preparing to Restore a Database Restoring Backups Restoring Databases from Different Backup Types Restoring Damaged System Databases 43

44 SQL Server Recovery Process BEGIN BEGIN COMMIT BEGIN CHECKPOINT BEGIN COMMIT BEGIN COMMIT BEGIN COMMIT COMMIT Committed transactions are rolled forward and written to the database Uncommitted transactions are rolled back and are not written to the database 44

45 SQL Server Activities During the Restore Process Performs a Safety Check Database already exists Database files are different Database files are incomplete Recreates the Database and All Associated Files 45

46 Preparing to Restore a Database Verifying Backups Performing Tasks Before Restoring Backups 46

47 Verifying Backups RESTORE HEADERONLY Statement Returns header information of a backup file or backup set RESTORE FILELISTONLY Statement Returns information about the original database or transaction log files RESTORE LABELONLY Statement Returns information about the backup media RESTORE VERIFYONLY Statement Verifies that individual files are complete and readable 47

48 RESTORE HEADERONLY Statement Information: The backup file or backup set name and description The type of backup media that was used, such as a tape or hard disk The backup method, such as a full database, differential, transaction log, or file backup The date and time that the backup was performed The size of the backup The sequence number of a particular backup within a chain of backup files 48

49 RESTORE FILELISTONLY Statement The logical names of the database and transaction log files The physical names of the database and transaction log files The type of file, such as a database or a transaction log file The filegroup membership The backup set size, in megabytes (MB) The maximum allowed file size, in MB 49

50 Verifying Backups USE master GO RESTORE HEADERONLY FROM AWBackupDev GO RESTORE FILELISTONLY FROM AWBackupDev GO RESTORE LABELONLY FROM AWBackupDev GO RESTORE VERIFYONLY FROM AWBackupDev GO RESTORE HEADERONLY FROM DISK='c:\AdventureWorks1a.bak GO RESTORE FILELISTONLY FROM DISK='c:\AdventureWorks1a.bak GO 50

51 Performing Tasks Before Restoring Backups Restrict Access to the Database Limit access to members of the db_owner, dbcreator, or sysadmin role Back Up the Transaction Log Ensures database consistency Captures changes between the last transaction log backup and when the database was taken offline 51

52 Restoring Backups Using the RESTORE Statement Initiating the Recovery Process Specifying Restore Options 52

53 Using the RESTORE Statement USE master RESTORE DATABASE AdventureWorks FROM AWBackupDev Restoring Damaged User Databases You do not need to drop the damaged database SQL Server automatically recreates the database files and objects 53

54 Initiating the Recovery Process Specifying the RECOVERY Option Use with the last backup to be restored Allows access to database Specifying the NORECOVERY Option Use with all backup files except for the last backup to be restored Prevents access to database 54

55 Specifying Restore Options RESTORE option Description FILE RESTART Restores a specific backup You must specify a file number Continues an interrupted recovery operation MOVE TO REPLACE Specifies where to restore the backup files Use to restore to different disk, server, or standby SQL Server Replaces an existing database SQL Server does not perform a safety check 55

56 Restoring Databases from Different Backup Types Restoring from a Full Database Backup Restoring from a Differential Backup Restoring a Transaction Log Backup Restoring from a File or Filegroup Backup 56

57 Restoring from a Full Database Backup When to Use Physical disk is damaged Entire database is damaged, corrupted, or deleted To maintain an identical copy of database on another SQL Server Specifying Recovery Options Initiate the recovery process with the RECOVERY option (no TLB) Postpone the recovery process with the NORECOVERY option (next TLB) USE master RESTORE DATABASE AdventureWorks FROM AWBackupDev WITH FILE = 2, RECOVERY 57

58 Restoring from a Differential Backup Restores Only the Parts of the Database That Have Changed Since the Last Full Database Backup Returns the Database to the Exact State It Was in When the Differential Backup Was Performed Takes Less Time Than Applying a Series of Transaction Logs Syntax is the same as when you restore a full database Specify the backup file that contains the differential backup USE master RESTORE DATABASE AdventureWorks FROM AWBackupDiff WITH NORECOVERY 58

59 Restoring a Transaction Log Backup AdventureWorks Database Backups Full Database Differential Differential Data Log Log Log Log Log Log Log Database Damaged Restore AdventureWorks Database Full Database Differential USE master RESTORE LOG AdventureWorks FROM AWBackupLog WITH FILE = 2, RECOVERY Data Log Log Log 59

60 Specifying a Point in Time AdventureWorks Database Backups Full Database Differential Differential Data Log USE Log master RESTORE LOG AdventureWorks FROM AWBackupLog WITH FILE = 2, RECOVERY, Database Damaged STOPAT = November 12, :00 AM' Log Log Log Log Log Restore AdventureWorks Database Full Database Differential Data Log Log Log Log 60

61 Restoring from a File or Filegroup Backup Apply All Transaction Logs Since the File Backup Restore Filegroup Backups Containing Indexes and Tables as One Unit USE master RESTORE DATABASE AdventureWorks FILE = AWFile2 FROM AWFile2Backup WITH NORECOVERY 61

62 Restoring Damaged System Databases Restoring System Databases from a Backup Rebuilding System Databases (REBUILDDATABASE option in Setup.exe) Attaching or Restoring User Databases Restore from a backup Attach with sp_attach_db or sp_attach_single_file_db system stored procedure 62

63 Recommended Practices Obtain Information About Backups Before You Restore Specify NORECOVERY on All Except the Last Backup Use RECOVERY on the Last Backup to Return the Database to a Consistent State Add a Log Mark Before Performing a High-Risk Operation Test Backup Files Periodically By Using RESTORE VERIFYONLY 63

64 Restoring Databases Review SQL Server Recovery Process Preparing to Restore a Database Restoring Backups Restoring Databases from Different Backup Types Restoring Damaged System Databases 64

65 Thank you for your attention! Questions?