Database Files

Chapter 16. Accessing

Database

Files

 

 

 

 

 

 

 

 

 

You

can

access

a

database

file

from

your program by associating t

with

the

device

DISK

in

the appropriate

file

specification.

 

DISK

files

of

an

ILE

RPG program

also

associate

with distributed

da

(DDM)

files,

which

allow

you

to access

files on

remote

systems as

d

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Database Files

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Database

files

 

are objects

of

type

*FILE

on

the

AS/400. They can be e

ical or logical files and either externally described

or program-des

access database

files

by

associating

the file name with the devic

36 through

42

of

the

file

description

specifications.

 

 

 

Database files can be created by OS/400 Create File commands. For m mation on describing and creating database DB2files,UDBreferfo toAS/400the Database Programming manual and theDDS Reference.

Physical Files and Logical Files

Physical files contain the actual data that is stored on the system, a description of how data is to be presented to or received from a contain only one record format, and one or more members. Records in files can be externally or program-described.

A physical file can have a keyed sequence access path. This means presented to a program in a sequence based on one or more key fi

Logical

files

do not contain data. They

contain a

description

of

record

one

or

more

physical

files. A

logical

file

is

a

view or

representat

physical

files.

Logical

files

that

contain

more

than

one

format

are

r

multi-format

logical files.

 

 

 

 

 

 

 

 

 

 

 

If your program processes a

logical

file

which

contains

more

than

on

format,

you

can

use

a

read

by

record format

 

to

set

the format

y

Data Files and Source

Files

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A data

file

contains

actual

data,

or a view of the

data.

Records

in

grouped

into

members.

All

the

records

in

a

file

can be

in

one

membe

be grouped into different members. Most database commands and opera

default

assume that database

files

which onlycontainone memberdata.haveThis

 

means that when your program accesses

database

files

containing

data

need

to specify

the

member

name for

the file

unless

your

file

con

one

member.

If

your

file contains

more

than

one

member

 

and

a partic

is not

specified, the

 

first

member

is

used.

 

 

 

 

 

Usually, database files that contain source programs are made up of member. Organizing source programs into members within database files

you to better manage your programssource member. The contains source state- ments that the system uses to create program objects.

Copyright IBM Corp. 1994, 1999

281

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IBM AS/400 manual Accessing, Database Files, Physical Files and Logical Files, Data Files and Source
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AS/400 specifications

The IBM AS/400, now known as the IBM iSeries, is a midrange computer system that has been a cornerstone of enterprise computing since its introduction in 1988. Designed to provide a robust platform for business applications, the AS/400 is celebrated for its reliability, scalability, and integrated database capabilities.

One of the key features of the AS/400 is its Integrated Operating Environment, which blends hardware and software resources seamlessly. This integration allows businesses to execute diverse workloads, ranging from traditional applications to modern web-based services, all on a single platform. The operating system, OS/400 (now IBM i), offers a rich set of APIs and tools for developers, simplifying application development and management.

Another standout characteristic of the AS/400 is its built-in database, DB2 for i. This powerful relational database management system allows for efficient data handling and provides advanced features such as support for SQL, XML, and JSON, making it easier for businesses to manage their data and integrate it with other systems. The database's tight integration with the operating system enables high performance and security.

In terms of scalability, the AS/400 can accommodate small businesses as well as large enterprises, with the ability to support hundreds of users simultaneously. Its architecture allows for easy upgrades in hardware, meaning that organizations can scale their systems without replacing the entire infrastructure.

Security is another critical attribute of the AS/400. With a sophisticated security model, it offers built-in user authentication, access control, encryption, and auditing capabilities to protect data and applications from unauthorized access.

The AS/400 also supports multiple programming languages, including RPG, COBOL, Java, and PHP, giving organizations the flexibility to choose the development tools that best fit their needs. This diversity helps maintain legacy applications while also developing new ones that leverage modern technologies.

Moreover, the platform supports both traditional green-screen interfaces and modern graphical user interfaces, allowing organizations to transition smoothly into contemporary user experience paradigms.

Overall, the IBM AS/400 stands out as a resilient, flexible, and secure computing platform that enables organizations to effectively manage their business operations, streamline processes, and adapt to changing market demands. Its unique combination of integrated features and capabilities ensures that it remains relevant in today's fast-paced technology landscape.
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