12.2. Preventing and detecting corruption

Before we go too much further, it's important to define corruption as it relates to a SQL Server database. There are essentially two different types of corruption: logical and physical. Logical corruption refers to situations in which people (or applications) remove data they shouldn't—for example, deleting one half of an Order:OrderDetail relationship. In contrast, physical corruption is almost always caused by faulty I/O subsystem components; examples include crashed hard drives and faulty RAID controllers.

Making the distinction between logical and physical corruption is important. A statement from a DBA to the effect of "The database is corrupt!" usually means something much more sinister than the ...

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