Databases Reference
In-Depth Information
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Data managed independently of programs.
The people who use data are
normally not those who manage it.
•
Complexity of database technology.
To be effective in designing, oper-
ating, and using databases requires different(sometimes higher-level)
skills from those required for non-database technology.
•
Concurrent use of data.
Two or more users can access and use the same
data item concurrently. Without proper controls, improper processing
of data may occur.
•
Complexity of database structure.
There are three general types of data
structure: hierarchical, network, and relational. All three types cur-
rently require a series of indexes and pointers that permit users to
view the data from their individual perspectives. The more options
available to the users, the greater the complexity of the data structure.
In complex data structures, it is not uncommon for half of the total
space allocated to the database to be used for indexes and pointers.
The addition, deletion, and modification of data can literally require
hundreds of these indexes and pointers to be changed. Improper data
structure can thus make a database unresponsive to user needs.
•
The sophisticated use of
databases can involve multiple users accessing, modifying, entering,
and deleting data concurrently. Some of these processes are complex
and occur in stages. Thus, at any time, various transactions are in var-
ious stages of processing, making database recovery difficult.
• The database environment can fail for a variety of reasons, including
hardware failure, application system failure, operating system failure,
database management system (DBMS) failure, loss of integrity of data-
base, and operator failure. Adding to the complexity of recovery is the
size of the database and the time required to recover. In large, sophis-
ticated databases, recovery may require many hours or even days.
Complexity of database recovery procedures.
•
Extensiveness of backup data.
Databases can encompass many billions
of bytes or characters of data. Stored on magnetic media, such data is
often susceptible to loss. Thus, two factors must be considered in pro-
viding database backup. The first factor is the time frame in which re-
covery must occur. (The need for quick recovery requires frequent
copies of the database.) The second factor to be considered is the vol-
ume of data in the database. (Large databases require large amounts
of time to copy.)
•
Nonstandard DBMSs.
The file structure, access methods, and operating
characteristics of DBMSs can vary from vendor to vendor and even
within a single vendor. Because there is little uniformity between the
operation of various databases, it is not always possible to pull out
one database and plug in another. Individuals trained in one DBMS
sometimes require additional training to deal effectively with another.
The lack of standardization creates difficulties for auditors who have
audit responsibilities for DBMSs from more than one vendor.
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