Backup,Restore and Recovery. Training Division New Delhi

Transcription

1 Backup,Restore and Recovery Training Division New Delhi

2 Backup Restore and Recovery Backup Restore and Recovery No Data loss and server stay up and running Fault Tolerance protection Disk mirroring RAID Implement Hardware RAID solution Use window NT server s in-built capabilities Backup and Recovery of Data:Allows for the complete restoration of data over a wide range of potential system problem such as: Media Failure Database/Table Corruption Permanent loss of Server User Errors Moving/Copying to another server

3 Planning to Backup & Restore Backup and restore operation must be planed together. Think of the type of problem that might possibly affect the system e.g. Server failure, Database failure, Table corrupt Impotence of Data Recover to the point of failure, Can rely on last backup What downtimes is acceptable Requires more frequent backup Warm standby server

4 Analyzing Backup Requirment How large is each database? Sp_spaceused Dbcc sqlperf (logspace) How often does the data change? Are some table modified more then others? How easy would it be to re-create lost data? Do you need to keep a rotating sets of backup?

5 Backup Consideration Who is responsible for backup? Capability of executing the backup and restore command Member of db_owner or db_backupoperator roles. Verify that the backups are good Run consistency check before backup start. Periodically test backups by restoring on a testing server. Which database should you backup? System database User database

6 Types of backups Complete Database backup Copy the data as well as active transaction log. Differential Database Backup It is copy of only the changes to the database since the last full database backup. Only the last differential backup restore. Required full backup to be restored first. Transaction log It is a copy of all committed transaction since the last log backup

7 Type of Backup cont. Is a serial record of all database tranaction that can be replayed. It can restore database to known state. File and File group Backup Can be considered a vertical backup.

8 Backing up System Database Master Backup after any significant changes are made e.g. server configuration change,creating, changing and droping database or devices. Can t perform transaction log backup. MSDB Keep Information used by SQL Server Agent e.g. Job scheduling, alters.

9 Backing up System database Model Is a template database Backup when changing settings Tempdb Backup not required.

10 Backing up User Database At a minimum: Weekly backup of full database Daily transaction log backup Backup full database after: Non-logged operation Importing/exporting Select into/bulkcopy operation

11 Choosing backup Strategy Backup the database only You might lose all committed transaction that have accord after recent database backup. Backup all the data regardless of whether it changes after the last database backup. Is self-contained and does not rely on any other backup to be restored. It will use more space and time to complete backup operation on per backup. Set truncate log on checkpoint.

12 Choosing backup Strategy Backup data +Transaction log If is not acceptable to loss any transaction. You will be able to recover all committed transaction up to the point of failure. Provide the information necessary to redo changes made after a database backup was performed. If data changes are frequent. Creating and applying is more complex than simple database backup. Restoration for transaction log takes longer times.

13 Choosing backup Strategy Differential Database Backup Increase the speed of backup and restore. Record only those changes made to the database after the last full backup. It is a smaller and takes less time to complete. Don t allow to be restored to the exact point of failure.

14 Implementing backups Creating a backup devices Backup device enable to associate a logical name with the physical backup media. Tape device : Must be connected physically to the computer runs SQL server. Disk device : Are files on hard disk and are same as o/s files. \\server name\share name\path\file. Appropriate Permission. Backup data on network can be subject to error, verify it. Named pipe device : Third party vendors. Multiple device

15 Implementing backups Adding Backup Device Transact-SQL Sp_addumpdevice tape/disk,logical name, physical name. Backup database database_ name to device_name Backup database database_name to disk = path Enterprise manager Management->Backup->New backup device.

16 Implementing backups Verifying Database Consistency Database DBCC CHECKDB ( 'database_name' [, NOINDEX { REPAIR_ALLOW_DATA_LOSS REPAIR_FAST REPAIR_REBUILD }] ) [WITH {ALL_ERRORMSGS NO_INFOMSGS}] Tables DBCC CHECKTABLE table name Logs DBCC CHECKLOG log file name

17 Backing up the Database Through t-sql BACKUP DATABASE TO <backup_device> [,...n] [WITH [BLOCKSIZE = [[,] DESCRIPTION = [[,] DIFFERENTIAL] [[,] EXPIREDATE = RETAINDAYS = [[,] FORMAT NOFORMAT] [[,] {INIT NOINIT}] [[,] MEDIADESCRIPTION = [[,] MEDIANAME = [[,] [NAME = [[,] {NOSKIP SKIP}] [[,] {NOUNLOAD UNLOAD}] [[,] [RESTART] [[,] STATS [= percentage]] ] Through Enterprise Manager

18 Backing up Restriction Some operation are not allowed such as: Creating or deleting files. Creating indexes. Performing Non-logged operation. Shrinking Database.

19 Backup transaction LOG Through T-SQL BACKUP LOG { [WITH { NO_LOG TRUNCATE_ONLY }] TO <backup_device> [,...n] [WITH [BLOCKSIZE = [[,] DESCRIPTION = [[,] EXPIREDATE = RETAINDAYS = [[,] FORMAT NOFORMAT] [[,] {INIT NOINIT}] [[,] MEDIADESCRIPTION = [[,] MEDIANAME = [[,] [NAME = [[,] NO_TRUNCATE] [[,] {NOSKIP SKIP}] [[,] {NOUNLOAD UNLOAD}] [[,] [RESTART] [[,] STATS [= percentage]] ] }

20 Transaction Log Sql Server guarantee transaction atomicity and durability. Transaction function as a single unit of work. Guarantee that the changes are permanent. SQL Server writes every database changes to the transaction log. The log contain a record of every activity that changed the database. Keep tracks of new objects, user,permission changes.

21 Transaction Log Structure Records of transaction serves three function Recovery of individual transaction. Recovery of all incomplete transaction when SQL Server is started. Rolling a restored database forward to the point of failure.

22 Transaction Log backup The starting point of transaction backup is where: The previous transaction log backup ended. The transaction log backup as part of the most recent database or differential database backup ended. Truncating the transaction log: The inactive portion of the transaction log is that part of log which is no longer used during recovery process.

23 Transaction Log backup The ending point of inactive portion of the transaction log is the earlist of these events: The most recent checkpoint. A transaction that has not been committed or rolled back.

24 Condition for backing up Transaction log If the truncate log on check point is set to true. If any Non-logged operation have accured in the database. Until a database backup has been created. If the transaction log has been truncated, unless a database backup is crested. If any files are added or deleted from the database.

25 Checkpoint Execute Checkpoint startement Database option changed Server stopped, shutdown Reduce Recover interval

26 Restoring the database Through T-SQL Restore database database-name from device-name E DATABASE [FROM <backup_device> [,...n]] [WITH [DBO_ONLY] [[,] FILE = file_number] [[,] MEDIANAME = [[,] MOVE 'logical_file_name' TO 'operating_system_file_name'] [,...n] [[,] {NORECOVERY RECOVERY STANDBY = undo_file_name}] [[,] {NOUNLOAD UNLOAD}] [[,] REPLACE] [[,] RESTART] [[,] STATS [= percentage]] ]

27 Restoring the database Through Enterprise Manager Some restore command Restore headeronly from backup-device Restore filelistonly from backup-device Restore verify only from backup-device

28 Restoring Transaction Log Through T-SQL RESTORE LOG [FROM <backup_device> [,...n]] [WITH [DBO_ONLY] [[,] FILE = file_number] [[,] MEDIANAME = [[,] {NORECOVERY RECOVERY STANDBY = undo_file_name}] [[,] {NOUNLOAD UNLOAD}] [[,] RESTART] [[,] STATS [= percentage]] [[,] STOPAT = ] Through Enterprise Manager

29 Automatic Recovery It process each database in the following order at startup: master,model,tempdb,msdb, user database Manual When Disk failure Install windowsnt and load appropriate service pack, verify that appropriate domain functionality exist. Install SQL server and load appropriate service pack. Restore master, msdb backup. Shutdown the server Reconfigure the server for network libraries. Check SQL server running properly. Restore the user databases.

30 Recovery Recovery to prior state. Apply database backup. Apply sequence of transaction log. Restore to point of failure. Backup the current active transaction log. backup log mydb to disk= "c:\backup\mydblog1.bak" with no_truncate Restore database backup without recovery. restore database mydb from disk = "c:\backup\data.bak" with replace,norecovery Apply each transaction log backup in sequence. Apply the current transaction log file. restore log mydb from disk ="c:\backup\mydblogrp.bak" with recovery