database 6

extent

a contiguous section of disk storage space

data type

a detailed coding scheme recognized by system software such as dbms for representing organizational data

pointer

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

hash index table

a file organization that uses hashing to map a key into a location in an index where there is a pointer to the actual data record matching the hash 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 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 numer

redundant array of inexpensive disks

a set of physical disk drives that appear to the database user 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 other 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 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

distrubuting the columns of a table into several seperate physical records

horizontal partitioning

distrubuting the rows of a table into several separate files

secondary key

one field or combination of fields for which more than one record may have the same combination of values, also a unique key

page

the amount of date read or written by an operating system in one secondary memory disk input or output operation. for i/o with a magnetic type, the equivalent term is record block

blocking factor

the number of physical records per page

denormalization

the process of transforming normalized relations into normalized physical record specifications

stripe

the set of pages on all disks in a raid that are the same relative distance from the beginning of the dsk drive

field

the smallest unit named application data recognized by the system software

indexed file organization

the storage of records either sequentially or non sequentially with an index that allows software to locate individual records

sequential file organization

the storage of records in a file sequence according to a primary key value