Lisa has learned that most databases implement concurrency controls. What is concurrency, and why must it be controlled?

A.
Processes running at different levels, which can negatively affect the integrity of the database if not properly controlled.

B.
The ability to deduce new information from reviewing accessible data, which can allow an inference attack to take place.

C.
Processes running simultaneously, which can negatively affect the integrity of the database if not properly controlled.

D.
Storing data in more than one place within a database, which can negatively affect the integrity of the database if not properly controlled.

Explanation:
C: Databases are commonly used by many different applications simultaneously and many users interacting with them at one time. Concurrency means that different processes
(applications and users) are accessing the database at the same time. If this is not controlled properly, the processes can overwrite each other’s data or cause deadlock situations. The
negative result of concurrency problems is the reduction of the integrity of the data held within the database. Database integrity is provided by concurrency protection mechanisms.
One concurrency control is locking, which prevents users from accessing and modifying data being used by someone else.
A is incorrect because concurrency refers to processes running simultaneously, not at different levels. Concurrency issues come up when the database can be accessed at the
same time by different users and/or applications. If controls are not in place, two users can access and modify the same data at the same time, which can be detrimental to a dynamic
environment.
B is incorrect because the ability to deduce new information from reviewing accessible data occurs when a subject at a lower security level indirectly guesses or infers data at a
higher level. This can lead to an inference attack. It is not related to concurrency. Concurrency has to do with integrity, while inference is related to confidentiality.
D is incorrect because storing data in more than one place is not a problem with concurrency. Concurrency becomes a problem when two subjects or applications are trying to
modify the same data at the same time.