Using Program-Described Disk Files

no record blocking is done by the compiler, nor by data management. I keyword BLOCK is not specified, then default blocking occurs as descri

The input/output and device-specific

feedback

of the

file

information

are

not

updated

after each

read

or

write

(except

for

the RRN

and

on block

reads)

for files in

which

the records are blocked and unbloc

RPG compiler. The feedback area is

updated each time a block of re

ferred. (For further details on the

file informationILE

dataRPG

forstructure

s

AS/400

Reference.)

 

 

 

 

 

 

 

 

You can obtain valid updated feedback information by preventing the fi blocked and unblocked. Use one of the following ways to prevent blocki

¹ Specify BLOCK(*NO) on the file description specification.

¹At run time, use the CL command OVRDBF (Override with Database File) SEQONLY(*NO) specified.

Using Program-Described Disk Files

Program-described files, which are identified by an F in position 22 description specifications, can be described as indexed files, as se as record-address files.

Indexed File

An indexed file is a program-described DISK file whose access path i values. You must create the access path for an indexed file by usi description specifications.

An indexed file is identified by an

I

in

position

35 of

the

file

d

tions.

 

 

 

 

 

 

 

 

The

key fields identify

the records

in

an

indexed

file.

You

specif

key

field in positions 29

through 33,

the

format of

the

key

field

i

the starting location of the key field in the KEYLOC keyword of the f specifications.

An indexed file can be processed sequentially by key, sequentially wi randomly by key.

Valid

Search

Arguments

 

 

 

 

 

 

 

 

 

 

 

 

For

a program-described file,

a search

argument

must be a single fiel

CHAIN

and

DELETE

operations,

the

search

argument must be the same length

the

key

field that is defined on the

file

description

specifications

For

the

other file operations, the search argument may be a partial

The

DDS

specifies the fields to be

used

as

a

key

field.

The

KEYLOC

the

file description specifications specify the

starting

position

of t

The

entry in positions 29 through 33

of

the

file

description

specific

specify

the length of the key as defined

in the

DDS.

 

 

 

Figure 141 on

page 289 and

Figure 142

on

page 289

show

examples

of

how

use

the

DDS

to describe

the

access

path

for

indexed

files.

 

288 ILE RPG for AS/400 Programmer's Guide

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IBM AS/400 manual Using Program-Described Disk Files, Indexed File, Valid
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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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