T 4.28 Loss of data in a database

A loss of data in a database can be caused by a wide variety of reasons. These reasons can range from inadvertent manipulations of the data (for example by accidentally deleting data) to a database crash, for example as a result of a lack of storage space on a medium, or even to deliberate attacks.

A storage medium can only store a limited amount of data. This is also true for a database that needs to access a physical storage medium to store its data permanently. When this storage medium is full, the database may crash and result in a loss of data.

The capacity of the storage medium can become exhausted for various reasons. Examples include errors in application programs, increased storage demands by users, or even directed attacks in which the storage space available is deliberately reduced, for example to disable the system's logging capabilities.

Regardless of the cause, the result is always the same: the inability to guarantee the availability and completeness of the data, which in turn can have the following consequences:

• Certain applications that depend on the data in the database may not be able to run at all any more or may not provide all functionality.
• The information contained in the data may become incomplete.
• It could involve a great deal of effort to recover and restore the data destroyed.

Depending on cause of the data loss, it may be difficult or impossible to determine which data has been lost. This can result in additional financial losses or pose additional security risks.

Example:

When changes are made to a database model in the framework of a migration concept, the old tables and structures must be backed up first before they can be deleted. The new tables are then created after deletion. The old data resources now need to be converted and inserted into the modified tables. Errors in these procedures can quickly lead to a loss of data or the inability to insert the data in the tables.