الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
The designer of a database system faces many difficult probl
ems. Examples of these problems are :
Designing a physical data structure that facilitates rapid
search time and convenient update
Saving data integrity.
Maintaining data security and privacy; and
Achieving data independence.
This thesis studies the objectives of a database system.
It surveyes the main physical structures and addressing techn
iques for single—key and multikeyed files. It focuses on the
problem of coordinating concurrent accesses and updates to a
database in a multiuser environment while preserving the data
integrity. It surveys practical solutions to the concurrency
control problem. A multiuser multikeyed access method is desig
ned and implemented. It is proposed for PDP-11 computers running
under the Resource Sharing Time Sharing /Extended (RSTS/E) operat
ing system. The proposed access method provides a multikeyed file
structure that Basic-Plus users can access and update in a, sequ
ential or random order using any of t,.,ro keys. The proposed access
method supports multiple concurrent accesses and updates to
multikeyed files while preserving the database integrity. This
is achieved through the provision of a concurrency control mecha
nism that enforces transactions to follow deadlock-free locking