T 4.26 Failure of a database

Users usually first become aware of the failure of a database when the database management system (DBMS) used to display the data in the database fails to react. The failure may have been triggered by scheduled events such as maintenance work or by unforeseen events. Unforeseen events include, for example, problems with the hardware, software, or network. Software bugs, force majeure, negligence, or sabotage are also possible causes of such database failures.

The consequences to a user or an application when a database is not available any more can be far-reaching depending on the purpose and importance of the database. Applications that depend on the data in the database will only have limited operation or may not even operate at all. The users of these applications will not be able to perform some of their tasks, possibly even none at all, if these tasks cannot be performed using other resources. Depending on the types of tasks that can only be performed using the database in conjunction with IT support, the following consequences are possible, among others:

• Financial loss
• Personal injury
• A loss of trust by the customers or partners because contracted services cannot be supplied
• Limited operations or a complete failure of operations

Examples:

• An electronic archive uses a database in which all archived documents are indexed. When this index database fails, it becomes impossible to find or search for archived documents. The result is that the archive cannot be operated at all or is only able to provide limited operability.
• The content as well as all additional information for a regularly appearing publication were moved in their entirety to a database. Since a minimum of read access to this database is necessary for the corresponding department to do its work, the department will be not able to work on the content of the publication if the database does not function correctly. After the database was shut down to perform scheduled routine maintenance, unexpected delays in the maintenance work caused the database to be unavailable for longer than planned. The department was only able to perform very limited amounts of work on the content of the publication for a whole week because an alternate database was not available.
  • A publicly available database is overloaded by an enormous number of simultaneously submitted queries to the point where normal access to the database becomes almost impossible.