week 9 – chapter 8 - methods to backup databases - types of data to be backed up - recovery models...

Week 9 – Chapter 8

- Methods to Backup Databases

- Types of data to be backed up

- Recovery models

- Recovery methods

Methods to Back up Data

• Maintenance Wizard (Chapter 7) to create maintenance plan with scheduled backups

• Enterprise Manager to schedule job to perform backup or to perform unscheduled backup as required

• T-SQL commands

• Specialized packages such as Backup Exec or Arcserv (not discussed here)

Prevent Loss of Data

Have a strategy:1.To minimize data loss (malicious use of

delete, update statement, viruses, natural disaster, theft)

2.To recover lost data3.To restore data with minimal cost and

impactBackup regularly:

1.Backup frequently if your database is OLTP

2.Backup less frequently if your database is OLAP

Database Recovery Models

Set Database Recovery Model:• Full Recovery Model • Bulk logged recovery model• Simple Recovery Model

Modify a database recovery model1.Alter database pubs 2.Set recovery to bulk_logged

Backups

• SQL Server allows backups to occur while users continue to work with the database

• Backs up original files and records their locations

• Captures in the backup all database activities that occur during the backup process

Who can perform backup?1.Members of the sysadmin fixed server role2.Members of the db_owner and

db_backupoperators fixed database roles

Where to store backup?1.Hard disk file2.Tape3.A location identified by a Named Pipe (3rd

party software package)

Backups (ctd)

When to backup System Databases

• After modifying the master database:• Using CREATE DATABASE, ALTER

DATABASE or DROP statement• Executing certain Stored Procedures

• After modifying the msdb database• After modifying the model database

When to backup User Databases

• After creating a database• After creating an index• After creating a transaction• After performing un-logged operations:

• BACKUP WITH TRUNCATE_ONLY OR NO_LOG OPERATIONS

• SELECT INTO statement

Restricted Activities during backup

• Creating or modifying database• Performing autogrow operations• Creating indexes• Performing non-logged options• Shrinking a database

Create a Backup device

• A backup file that is created before it is used for a backup is called a backup device

• Why create permanent backup devices?• To reuse backup files for future

backups• To automate the backup

Create a Backup device(ctd)

Use sp_addumpdevice system procedure:• Specify a logical name• Logical and physical Names are stored in the

sysdevices system table

Example:Use masterExec sp_addumpdevice ‘disk’ , ‘mybackupfile’, ‘c:\Backup|mybackupfile.bak’

Perform Backup without backup device

Why create backup without backup device?• To perform one time backup• To test backup operation that you plan to

automateHow to use backup database statement:

• Specify the media type (disk, tape, or Named Pipe)

• Specify the complete path and full Name

Example:Use masterBackup database NorthwindTo Disk = ‘c:\temp\mycustomers.bak’

Types of Backup Methods

• Full database backup

• Differential backup

• Transaction log backup

• File or File group backup

Full Database Backup

• Provides a baseline

• Backs up original files, objects and data

• Backs up portions of the transaction log

Example:

Use master

Exec sp_addumpdevice ‘disk’, ‘NwindBac’ ,

‘D:\mybackupdir\Nwindbac.bak’

Backup database Northwind to NwindBac

Full Database Backup Options

WITH INIT: overwrites any previous backup on that file

WITH NOINIT : appends the full database backup to the backup file. Any previous backup left intact.

Differential database backup

• Use on frequently modified databases• Requires a full database backup before• Backs up database changes since the last full

database backup• Saves time in both backup and restore

processes

Example:Backup Database NorthwindDisk = ‘D:\Mydata|Mydiffbackup.bak’WITH DIFFERNTIAL

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

Example:Use master

Exec sp_addumpdevice ‘disk’, ‘Nwindbaclog’,

‘D:\Baclup\Nwind backuplog.bak’

Backup log Northwind To NwindBaclog

Backup using No-truncate Option

No-truncate option:

• Saves the entire Transaction log even if the database is inaccessible

• Doesn’t purge the Transaction log of committed Transactions

• Allows data to be recovered up to time of system failure

Clear the Transaction log

• Use Backup statement to clear transaction log

• Use truncate only or no_log option• Can’t recover changes• Is not recorded changes

Database file or filegroup backup

1.Use on very large databases

2.Backup the database files individually

3.Ensure that all database files in File group are backed up

4.Back up transaction log

Example:

Backup database phoneorders

File = Orders2 To orderbackup2

Backup log phoneOrders to orderlog