Beginning Microsoft SQL Server 2008 ... - S3 Tech Training

❑ Differential: This might be referred to as a “backup since” backup. When you take a differential
backup, it only writes out a copy of the extents (see Chapter 9 if you’ve forgotten) that have
changed since you did the last full backup. These typically run much faster than a full backup
does and will take up less space. How much less? Well, that depends on how much your data
actually changes. For very large databases where backups can take a very long time to run, it is
very common to have a strategy where you take a full backup only once a week or even only
once a month, and then take differential backups in between to save both space and time.
❑ Transaction Log: This is again just what it sounds like: a copy of the transaction log. This option
will show up only if your database is set to Full or Bulk logging. (This option is hidden if you
are using simple logging.) Again, full discussion of what these are is coming up shortly.
A subtopic of the backup type is the backup component, which applies only to full and differential backups.
For purposes of this book, we should pretty much just be focused on backing up the whole database.
That said, you’ll notice another option titled Files and Filegroups. Back in our chapters on database
objects and creating databases, we touched briefly on the idea of filegroups and individual files for data
to be stored in. This option lets you select just one file or filegroup to participate in for this backup; I highly
recommend avoiding this option until you have graduated to the “expert” class of SQL Server user.
Again, I want to stress that you should avoid this particular option until you’ve got yourself something
just short of a doctorate in SQL Server Backups. The option is for special use, designed to help with very
large database installations (figure terabytes) that are in high-availability scenarios. There are major
consistency issues to be considered when taking and restoring from this style of backup, and they are
not for the faint of heart.
Backup Set
A backup set is basically a single name used to refer to one or more destinations for your backup.
SQL Server allows for the idea that your backup may be particularly large or that you may otherwise
have reason to back up across multiple devices — be it drives or tapes. When you do this, however, you
need to have all the devices you used as a destination available to recover from any of them — that is,
they are a “set.” The backup set essentially holds the definition of what destinations were involved in
your particular backup. In addition, a backup set contains some property information for your backup.
You can, for example, identify an expiration date for the backup.
Destination
This is where your data is going to be backed up to. Here is where you define one or more destinations
to be utilized for one backup set. For most installations this will be a file location (which later will be
moved to tape), but you can also define a backup device that would let you go directly to tape or similar
backup device.
Options
Chapter 19: Playing Administrator
In addition to those items we just covered from the General node of the dialog box, you also have a node
that lets you set other miscellaneous options. Most of these are fairly self-describing. Of particular note,
however, is the Transaction Log area.
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