Beginning Oracle Database 11g Administration From Novice to Professional

CHAPTER 13
Recovery
These Officers, with the Men belonging to the Engine, at their Quarterly Meetings,
discourse of Fires, of the Faults committed at some, the good Management in some
Cases at others, and thus communicating their Thoughts and Experience they grow
wise in the Thing, and know how to command and to execute in the best manner
upon every Emergency.
—Benjamin Franklin, in a letter to the Pennsylvania Gazette,
following a disastrous fire in Philadelphia in the 18th century
In the previous chapter, you learned how to make backup copies of the database. You
will now turn your attention to repairing the database if it gets damaged. For the purposes
of this chapter, you should assume the availability of backup copies made using
Recovery Manager (RMAN) but you will discover that backup copies are not the only
repair option available. You will also get acquainted with a powerful tool called Data
Recovery Advisor (DRA), which greatly simplifies the database administrator’s job.
Horror Stories
The following are true stories based on personal experiences.
Sometimes we make a mountain out of a molehill. Early in my career, in the days of
Oracle 7, a few blocks of data in the company’s most critical database were found to be
corrupted. Any transaction that touched the affected blocks could not complete, but the
database was otherwise functional. This was a large Enterprise Resource Planning (ERP)
database that the business depended on for all aspects of its functioning, so the application
administrators went into high gear. There were no disk backups because of the sheer size
of the database, so the application administrators recalled the tapes from the offsite storage
facility. They shut down the database at the end of the day and began restoring it from
tapes, hoping to have the database ready for business the next day. However, three- quarters
of the way into the restore operation, a defect was found in the tapes and the application
administrators had to requisition the previous set of tapes from the offsite storage facility.
The offsite storage facility was 100 miles away, and this necessitated a substantial delay.
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