Access speed can be essentially zero and constant, regardless of n, the number of records. This can be
expressed as O(k), where k is a constant of a small value. Such performance becomes possible because the
database management system stores data about the data (metadata) as well as the data itself.
Metadata also makes data stored in a database self-describing. This means that programs accessing the data
don??™t need to know so many details regarding how the data are stored. If a program reads from an ordinary file,
it must know about data types, formats, and the order of fields. However, when a program reads from a database,
it often needs only specify what information it requires.
A database also allows for efficient utilization of storage space. One of the consequences of good database
design is that duplication of data is minimized. When mass storage devices were more expensive, this virtue
was more important, but minimizing redundancy is still helpful in promoting efficiency, avoiding errors, and
protecting against corruption of data.
Database management systems (DBMS) also promote data security in a variety of ways. For instance, data
backup and recovery facilities are always built into the DBMS, and data can be copied to a backup medium,
even as the database continues to operate.
Pages:
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389