OVERVIEW OF MAJOR COMPONENTS - Database Design and Development: An Essential Guide for IT Professionals - page 50

tions. To accomplish these functions, the operating system uses hardware timers and
interrupts.

Process Management. The operating system executes database and other
operations as processes. A process is the lowest executable level of software. Say
that one of your users makes a request for data retrieval from the database. This is
a process for the operating system. If another of your users makes a request for his
or her data retrieval, that is another process. The operating system manages all such
processes by allocating resources, initiating and completing the processes, and
resolving deadlocks when processes compete simultaneously and wait for the same
resources.

Memory Management. The operating system coordinates the movement of data
in and out of the primary and cache memory of a computer. It maintains the free
memory space. It manages the memory hierarchy. Main memory is divided into
pages, and the memory manager of the operating system allocates memory pages
for the execution of the individual processes.

File Management. An important function of the operating system, file manage-
ment, controls and coordinates the structure and storing of data on secondary
storage. Files stored on disk drives and tape devices are under the control of the
file manager. Files are collections of data that are moved to and from main memory.
The file manager enables applications to create, delete, and insert data into files or
alter the contents of files. Suppose a file is mostly accessed in a sequential manner.
Then the data blocks of the file must be kept sequentially in disk storage on adja-
cent cylinders. Ealier mainframe operating systems allowed the systems program-
mers to control the placement of a file on specific cylinders. However, this control
placed a burden on the systems programmers to calculate and allocate the cylinders
needed for each file. Also, volatile files had to be reorganized frequently. But,
modern operating systems make disk organization transparent to the programmers
and manage the organization internally.

Input/Output Management. This area covers the setting up and maintaining of
logical channels or paths between processor tasks and workstations. The functions
encompass channel allocation and deallocation, channel setup, channel coordina-
tion, and remote data movement. Error detection and correction over the channels
are also part of I/O management. Physical links are initiated, and the data transfer
is controlled.

Network Control. Network management software manages the flow of data over
communications media. This is especially critical in distributed database environ-
ments. Major functions of network management include message routing, naming
schemes, addressing of nodes, protection against potential deadlocks of competing
data movements,

media access control, error detection and correction, and

communications setup.

Fault Detection and Recovery. The operating system monitors the overall system
for malfunctions, faults, and failures. When you consider a busy database environ-