OVERVIEW OF MAJOR COMPONENTS - Database Design and Development: An Essential Guide for IT Professionals - page 48

transmission of data. Note how these pieces are especially important in a database
environment.
Processor. Processors have become more powerful, faster, and cheaper. In a data-
base environment, the processors in the client workstations and the application
servers have to be powerful and fast. The processors in the client machines perform
instructions to present data to the users in many new and sophisticated ways. The
fast and powerful processors in the application servers must process complex
requests for data from the database. In a three-tier client/server architecture, data
storage and retrieval functions are separated out of application servers and the
database resides on separate database server machines.
Main Memory. When data are fetched from a database for processing, they are
initially brought into memory buffers and then moved through the processors. In a
database environment, you deal with movement of large volumes of data through
the memory buffers. Proper buffer management is essential. When a request is made
for data, the memory buffers are searched first to see whether the requested data
are already in the memory buffers as a result of prior data retrievals. If the data are
already found in the memory buffers, then the data could be accessed and used
much faster. Main memory that can accommodate many large buffers is conducive
to the performance of a database environment.
Input/Output Control. Computer systems use I/O (input/output) mechanisms to
move data into and out of the computer's main memory from secondary storage. A
typical sequence followed by I/O control for movement of data runs like this: select
the storage device, wait until the device is ready, transfer a piece of data from the
device I/O buffer to the processor's accumulator, transfer the data from the accu-
mulator into a memory location, reckon the next memory location, go back, and
repeat the steps until all requested data is moved into memory. When you deal with
high volumes of data in a database environment, you need sophisticated I/O control
to improve performance.
Tape Storage Devices. Content of databases is backed up regularly and used for
recovery if and when malfunctions destroy databases, fully or partially. Also, peri-
odically, parts of old data are archived and saved, sometimes at remote locations.
In small and medium-sized database environments, magnetic tapes serve as the
medium for backing up and saving the data. Although data can be stored and
retrieved sequentially, this restriction is not a handicap for content backup and
storage. In the modern database environment, compact tape cartridges are widely
used.
Communication Links. In earlier database environments of organizations, most
of the processing was done locally around a centralized database. Communication
links transferred data between the centralized database and the PCs or computer
terminals—all mostly at a single site. Today's database environments are different.
Distributed databases have become common. Client/server systems have spread
rapidly. Data communications move high volumes of data from distributed data-
bases to different locations, from the database server to the client workstations, and