Beginning Oracle Database 11g Administration From Novice to Professional

CHAPTER 12
Backups
As to our Conduct in the Affair of Extinguishing Fires, tho’ we do not want Hands or
Good- Will, yet we seem to want Order and Method, and therefore I believe I cannot
do better than to offer for our Imitation, the Example of a City in a Neighbouring
Province. There is, as I am well inform’d, a Club or Society of active Men belonging
to each Fire Engine; whose Business is to attend all Fires with it whenever they happen;
and to work it once a Quarter, and see it kept in order.
—Benjamin Franklin, in an anonymous letter to the
Pennsylvania Gazette (of which he was the editor), following
a disastrous fire in Philadelphia in the 18th century
American national hero Benjamin Franklin often wrote anonymous letters to the Pennsylvania
Gazette, a prominent newspaper that he himself owned and edited. In one such
letter he coined the famous phrase “an ounce of prevention is worth a pound of cure”
and, in addition to making several suggestions for the prevention of fires, he suggested
that Philadelphia imitate his native Boston in establishing fire stations and employing
firefighters; not only should all efforts be made to prevent fires but the city should be
adequately prepared to handle the next inevitable fire.
Backups are to a database what fire stations and fire fighters are to a city; we may
protect the database against damage the best we can, but we must be prepared if the
database ever gets damaged, through user or operator error or hardware failure, and
needs to be repaired. A backup is a snapshot of a database or a part of a database; if the
database is damaged, the damaged parts can be repaired using the backups. Archived
logs can be used in conjunction with backups to replay transactions that changed data
after the backup was performed. This chapter describes how to create various kinds of
backups; the next chapter describes how to use them to repair databases. The impatient
reader may note that a backup can be created with two simple words:
but, as the leading mind of the European renaissance, Leonardo da Vinci, said: “Those
who are in love with practice without knowledge are like the sailor who gets into a ship
without rudder or compass and who never can be certain whether he is going. Practice
must always be founded on sound theory.”
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