Database Administration Categories/Types of Failures

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CATEGORIES OF DATABASE FAILURES

There are different reasons for a database to fail .Some of them may result in a partial failure, some may become a complete disaster. There are many categories of failures among these are: * Media Failure

* User Error
* Database Instance Failure
* Statement Failure
* Process Failure
* Network Failure

MEDIA FAILURE

An error can occur when trying to write or read a file on disk that is required to operate an Oracle database. This occurrence is called media failure because there is a physical problem reading or writing to files on the storage medium.

EXAMPLE SCENARIOS
A common example of media failure is a disk head crash that causes the loss of all database files on a disk drive. All files associated with a database are vulnerable to a disk crash, including data files, control files, online redo logs, and archived logs.

SOLUTION
The appropriate recovery from a media failure depends on the files affected. Media failure is the primary concern of a backup and recovery strategy, because it typically requires restoring some or all database files and the application of redo during recovery. Multiplexing and Raid comes in handy in recovering from this situation.

USER ERROR
EXAMPLE SCENARIO
As an administrator, you can do little to prevent user errors such as accidentally dropping a table. SOLUTION
Often, user errors can be reduced by increased training on database and application principles. You can also avoid user errors by administering privileges correctly so that users are able to do less potential damage. Furthermore, by planning an effective recovery scheme ahead of time, you can ease the work necessary to recover from user errors. Typically, a user error such as a dropped table requires either re-entering the lost changes manually (if a record of them exists), importing the dropped object (if an export file exists), or performing incomplete recovery either of an individual tablespaces...
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