GLOSSARY - Introduction to Database Management - page 458

Nondeterministic function A function that might return different results, even if called
with exactly the same arguments.
Non-logged operation That means that the change isn't written to the transaction log,
but instead is made directly to the database.

Non-loss decomposition Normalization process in which neither data nor relation-

ships are lost.
Nonrepeatable read A condition where data changes between reads of the same

data set.
Nonvolatile storage Storage media that continues to hold the data it contains when
power is lost or the computer is turned off. The most common example is disk drives.

Normal forms Defined rules for data normalization.

Null value An undefined value, usually used to identify that no value is provided for

that attribute

Nullability Column definition as to whether or not a column can accept null values.
Object-oriented database model Database model where entities are treated as objects,
which are individual items that can be defined and described more completely than in a
relational model.

Object-relation model Data model based on both relational and object modeling

concepts.
Object-relational database model Hybrid database model based on the relational
model, but integrating features and functionality from the object-oriented model.

OLE DB A Microsoft data access API.
One-to-many relationship A relationships in which one referenced entity instance
can be related to any number of referencing entity instances.

One-to-one relationship A relationships in which one referenced entity instance can
be related to one referencing entity.
Online transaction processing Database type characterized by the need to support data
update, change, and delete data, the need to optimize for support of concurrency and
throughput, and the requirement to scale to meet the needs of a large number of users.

Open Database Connectivity (ODBC) An industry standard API Supporting data

connectivity.
Open transaction A pending transaction that has not been committed or rolled back.
Operating system software Software that controls the computer hardware, provides
an interface to the user, and provides an environment in which applications can run.

Operator precedence Operator ranking used to determine the order in which opera-

tors are processed.
Optimistic processing Transaction control method that assumes that conflicts are
unlikely and does not check for conflicts before processing the transaction.

OR Boolean operator used to test conditions in which the result is true if either condi-
tion is true.