Types of File Descriptions

RPG program

File name - FILEY

Device = SEQ

FILEY

File type =

DEVICE

Device type =

PRINTER

Figure 128.

Associating a file name with a display file description

 

 

Although

the

file name and

file type are coded

in the

RPG

program,

you can

change the type

of file or the device

used

in a

program

the program. To find out how, see “Overriding and Redirecting

File I

Output”

on

page 273.

 

 

 

 

Naming Files

On the

AS/400

system,

files

are

made up of members. These

files are

into libraries.

The convention

for naminglibraryfiles-name/fileis-name.

 

 

 

 

In an ILE RPG program, file names are identified in positions 7 thro

description

specifications.

File

names

can

be

up

to

ten

characters l

unique.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

You do not qualify the file

name

with a

library

within

a

program.

system searches

the

library

list

associated

with

your

job

to

find

to change the name, member,

 

or specify a particular library, you c

override

command.

See

“Overriding

and

Redirecting File

Input

and

Outpu

page 273

for more

information

on

file

overrides.

 

 

 

 

 

Types of File Descriptions

When identifying the file description your

program will be using, you

whether it is

a program-described

file or

an externally described

¹ For

aprogram-described file

, the

description

of the fields are coded

RPG

source

member

on input

and/or

output

specifications.

The description of the file to the operating system includes info where the data comes from and the length of the records in the

¹For anexternally described file , the compiler retrieves the description o

fields

from

an external file-description which was created using D

SQL commands.

Therefore, you do not have to code the

field

desc

input

and/or

output specifications within the RPG source member.

The

external

description includes information about where the data

such

as

the

database or

a specific device, and a

description

its

attributes.

The file

must exist and be accessible from

the

you

compile

your

program.

 

 

 

Externally described files offer the following advantages:

¹ Less

coding

in programs. If the

same file

is used by many

progr

can

be defined once to the operating system and used by

all t

This

practice eliminates the need to code input and output

speci

RPG

programs

that use externally

described

files.

 

Chapter 14. Defining Files263

Page 287
Image 287
IBM AS/400 manual Naming Files, Types of File Descriptions

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.