SQL Server 2008 R2 : Database Backup and Restore (part 4) - Backing Up a Database

Creating Database Backups with SSMS

The backup options in SSMS are accessible through the Object Explorer. For example, you can right-click the AdventureWorks2008 database in the SSMS Object Explorer, select Tasks and Backup, and a backup window like the one shown in Figure 2 appears.

Figure 2. The Back Up Database window in SSMS.

The Source section on the Back Up Database window contains information relative to the database that will be backed up. The target database is displayed in the first drop-down, along with the recovery model set for the database. The backup types available in the drop-down are dependent on the recovery model. For simple recovery, only full and differential backup types are available. For full recovery and bulk-logged recovery models, all backup types are available in the drop-down.

The Backup Set section allows you to give the backup a meaningful name and specify when the backup set will expire. When the backup set expires, the backup can be overwritten and is no longer retained. If the backup is set to expire after 0 days, it will never expire.

The Destination section identifies the disk or tape media that will contain the backup. You can specify multiple destinations in this section by clicking the Add button. For disk media, you can specify a maximum of 64 disk devices. The same limit applies to tape media. If multiple devices are specified, the backup information is spread across those devices. All the devices must be present for you to be able to restore the database. If no tape devices are attached to the database server, the Tape option is disabled.

You can select several different types of options for a database backup. Figure 3 shows the options page available when you back up a database by using SSMS.

Figure 3. The Back Up Database Options page in SSMS.

The Overwrite Media section allows you to specify options relative to the destination media for the backup. Keep in mind that a given media set can contain more than one backup. This can occur if the Append to the Existing Backup Set options is selected. With this option, any prior backups contained on the media set are preserved, and the new backup is added to it. With the Overwrite All Existing Backup Sets option, the media set contains only the latest backup, and no prior backups are retained.

You can use the options in the Reliability section to ensure that the backup that has been created can be used reliably in a restore situation. Verifying the backup when finished is highly recommended, but doing so causes the backup time to be extended during the verification. Similarly, the Perform Checksum Before Writing to Media option helps ensure that you have a sound backup, but again, it causes the database backup to run longer.

The options in the Transaction Log section are available for databases in the full recovery or bulk-logged model. These options are disabled in the simple recovery model. The Truncate the Transaction Log option causes any inactive portion of the transaction log to be removed after the database backup is complete.

The set of options in the Tape Drive section are enabled only when tape has been selected for the destination media. Selecting the Unload the Tape After Backup option causes the media tape to be ejected when the backup completes. This option can help identify the end of a backup and prevent the tape from being overwritten the next time the backup runs. The Rewind the Tape Before Unloading option is self-explanatory; it causes the tape to be released and rewound before you unload the tape. The last set of options relate to compressed database backups.

Creating Database Backups with T-SQL

The T-SQL BACKUP command offers a myriad of options to perform all the backup operations available in SSMS. However, SSMS does not support some backup operations that can be performed only with T-SQL.

The BACKUP command comes in three different flavors. The first flavor involves the backup of a database. The command syntax starts with BACKUP DATABASE, followed by the relevant parameters and options. The second flavor involves the backup of a file or filegroup that is part of the database. The command syntax for this type of backup also utilizes the BACKUP DATABASE command, but a file or filegroup is specified after the database name to identify which parts of the database should be backed up. The last flavor involves the backup of the database’s transaction log. The syntax for backing up the transaction log starts with BACKUP LOG. Each flavor shares many of the same options. The basic syntax for backing up a database follows:

BACKUP DATABASE { database_name | @database_name_var }
TO < backup_device > [ ,...n ]
[ [ MIRROR TO < backup_device > [ ,...n ] ] [ ...next-mirror ] ]
[ WITH
     [ BLOCKSIZE = { blocksize | @blocksize_variable } ]
     [ [ , ] { CHECKSUM | NO_CHECKSUM } ]
     [ [ , ] COMPRESSION | NO_COMPRESSION]
     [ [ , ] COPY_ONLY ]
     [ [ , ] { STOP_ON_ERROR | CONTINUE_AFTER_ERROR } ]
     [ [ , ] DESCRIPTION = { 'text' | @text_variable } ]
     [ [ , ] DIFFERENTIAL ]
     [ [ , ] EXPIREDATE = { date | @date_var }
     | RETAINDAYS = { days | @days_var } ]
     [ [ , ] PASSWORD = { password | @password_variable } ]
     [ [ , ] { FORMAT | NOFORMAT } ]
     [ [ , ] { INIT | NOINIT } ]
     [ [ , ] { NOSKIP | SKIP } ]
     [ [ , ] MEDIADESCRIPTION = { 'text' | @text_variable } ]
     [ [ , ] MEDIANAME = { media_name | @media_name_variable } ]
     [ [ , ] MEDIAPASSWORD = { mediapassword | @mediapassword_variable } ]
     [ [ , ] NAME = { backup_set_name | @backup_set_name_var } ]
     [ [ , ] { NOREWIND | REWIND } ]
     [ [ , ] { NOUNLOAD | UNLOAD } ]
     [ [ , ] RESTART ]
     [ [ , ] STATS [ = percentage
 ] ]
]


					  

The number of options is extensive, but many of them are optional. A BACKUP DATABASE command can be as simple as the following example:

BACKUP DATABASE [AdventureWorks2008]
 TO  DISK = N'C:\mssql2008\backup\AdventureWorks2008_COPY.bak'

The first part of the BACKUP command is related to the database you want to back up (database_name), followed by the location to which you want to write the backup (backup_device). The remainder of the syntax relates to the options that can be specified following the WITH clause. These options determine how your backup will be created and the properties of the resulting backup. Table 1 outlines these options.