Understanding Database Failure Types (Part I)
There are six general categories for database-related failures. Understanding what category a failure belongs in will help you to more quickly understand the nature of the recovery effort you need to use to reverse the effects of the failure and maintain a high level of availability and performance in your database.
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The six general categories of failures are as follows:
1- Statement:
A single database operation fails, such as a DML (Data Manipulation Language) Statement INSERT ,UPDATE , and so on.
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2- User process:
A single database connection fails.
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3- Network:
A network component between the client and the database server fails, and the session is disconnected from the database.
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4- User error:
An error message is not generated, but the operation's result, such as dropping a table, is not what the user intended.
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5- Instance:
The database instance fails unexpectedly.
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6- Media:
One or more of the database files is lost, deleted, or corrupted.
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In the next six sections, we'll provide details on these failure types and suggest some possible solutions for each failure type.
For one particular type of failure, media failure, we'll provide more detailed solutions for recovery later in this chapter.