Modern Database Management - Chapter 6

Extent

A contiguous section of disk storage space

Data type

A detailed coding scheme recognized by system software, such as a DBMS, for representing organizational data.

Pointer

A field of data that can be used to locate a related field or record of data.

Hashed index table

A file organization that uses hashing to the map a key into a location in a index, where there is a pointer to the actual data record matching the hashing key.

Physical record

A group of fields stored in adjacent memory locations and retrieved and written. together as a unit by a DBMS.

Physical file

A named portion of secondary memory (a magnetic tape pr hand disk.) allocated for the purpose of storing physical records

Tablespace

A named set of disk storage elements in which physical files for database tables may be stored.

Hashing algorithm

A routine that converts a primary key value into a relative record number ( or relative file address).

Redundant Array of Inexpensive Disks (RAID)

A set, or array of physical disk drives that appears to the database user (and programs) as if they form one large logical storage unit.

Hashed file organization

A storage system in which the address for each record is determined using a hashing algorithm.

Bitmap index

A table of bits in which each row represents the distinct values of a key and each column is a bit, which when on indicates that the record for that bit column position has the associated field value

Index

A table or data structure used to determine the location of rows in a file that satisfy some condition.

File organization

A technique for physically arranging the records of a file on secondary storage devices.

Join index

An index on columns from two or more tables that come from the same domain of values

Vertical partitioning

Distributing the columns of a table into several separate physical records

Horizontal partitioning

Distributing the rows of a table into several separate files

Secondary key

One field or a combination of fields for which more then one record may have the same combination of values. Also called a nonunique key.

Field

The Smallest unit of named application data recognized by system software.

Page

The amount of data read or written by an operating system in one secondary memory (disk) input or output (I/O) operation. For I/O with a magnetic tape, the equivalent term is record block.

Blocking Factor

The number of physical records per page.

Denormalization

The process of transforming normalized relations into unnormalized physical records specifications

Stripe

The set of pages on all disk in a RAID that are the same relative distance from the beginning of the disk drive.

Sequential file organization

The storage of record in a file sequence according to a primary key value.

Indexed file organization

The storage of records either sequentially or nonsequentially with an index that allows software to locate individual records