Using Sequential Files

Accessing Display Devices

You use display files to exchange information between

your

program

and

device

such as a

workstation. A display file is

used

to

define

the

mation

that

is

to

be

presented on a display, and to

define how

the

be

processed

by

the

system on its way to and

from

the

display.

 

See

Chapter 18,

“Using

WORKSTN Files” on page 331

for a

discussion

on

ho

use

WORKSTN

files.

 

 

 

 

 

 

 

Using Sequential Files

Sequential

files in

an ILE

RPG

program associate with any sequentially o

file on

the AS/400

system,

such

as:

¹Database file

¹Diskette file

¹Printer file

¹Tape file.

The

file name

of the SEQ file in

the

file

description

specifications

AS/400

file. The file description of the AS/400

file

specifies

the

act

e.g. tape, printer and diskette.

 

 

 

 

 

 

 

 

You

can also use the CL override

commands,

for

example

OVRDBF,

OVRDKTF

and

OVRTAPF, to

specify the actual

I/O

device

when

the program is

ru

Specifying a Sequential

File

 

 

 

 

 

 

 

 

 

 

A

sequential

(SEQ)

device

specification, entered

in

positions

36

through

file description specification, indicates that the input or output is

sequentially-organized file. Refer

to Figure 162

on

page 327.

The

actua

be associated with the file while running the

program can be

specifi

override

command

or by

the file

description that

is pointed to by t

SEQ

is specified

in a program, no device-dependent

functions

such

as s

or

CHAIN

can

be

specified.

 

 

 

 

 

 

The following figure shows the operation codes allowed for a SEQ file.

Table

26.

Valid File Operation Codes for a Sequential File

 

 

 

 

 

 

File

Description

Specifications

Calculation

Specifications Positions

 

Positions

 

 

 

 

 

 

 

 

 

 

 

17

 

18

 

 

26-35

 

 

 

 

 

 

 

I

 

 

P/S

CLOSE,

FEOD

 

 

 

 

 

 

 

 

I

 

 

F

READ,

OPEN,

CLOSE, FEOD

 

 

 

 

 

O

 

 

 

WRITE, OPEN, CLOSE, FEOD

 

 

 

 

 

 

 

Note: No print control specifications are allowed for a sequential file.

326 ILE RPG for AS/400 Programmer's Guide

Page 349 Page 351
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IBM AS/400 manual Accessing Display Devices, Using Sequential Files, Ovrdbf, Specifying a Sequential
Page 349 Page 351

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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