Database Reference
In-Depth Information
Developing a Backup Policy
Knowing how to makebackups of databases and how to restore them is fine. But these
skills will be of no use unless you put a system in place to make backups regularly and ef-
fectively. The value of backups is greatly diminished if you can't restore them without
clobbering databases in the process, without causing more loss of data, or if you can't
quickly restore them. To be effective as a database administrator, you should develop a
backup policy and and adhere to it.
A backup policy should be in writing, even if it's only for your use, and it should cover a
variety of aspects of making backups and being able to restore them. You'll have to devel-
op your own unique policy according to your situation, based on the value of the databases,
the sensitivity of the information, and other factors. For instance, if you have a database for
your personal website, a database for which you earn nothing, that no one else depends
upon, and one that you change rarely, your policy might be to make a complete backup
once a week and keep backups for at least a month. However, if you're the database admin-
istrator for a large site with millions of rows of data in many tables, a database that thou-
sands of people use every day and your employer uses to store credit card numbers from
transactions amounting to a significant amount of revenues, your backup policy will be
much more elaborate. You will address security, the effect that making a backup has on
user traffic, and how quickly data can be restored when needed. For our purposes, we'll de-
velop a backup policy that is somewhere in between these two extremes to give you a sense
of what you should consider.
The first step is to take inventory of the databases and tables for which you're responsible.
Let's use the two databases that we have been using for the examples throughout this topic.
However, so that the scenario is more meaningful, let's suppose that a couple of years have
passed and the bird-watchers website has attracted many more members. Based on that,
I've arbitrarily increased the row counts for most of the tables, and eliminated temporary
tables. Table14-1 lists the tables, grouped by database and sorted alphabetically, along with
an assessment of each table.
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