Overriding and Redirecting File Input and Output

Chapter 15. General

File

Considerations

This

chapter

provides information on the following aspects of file pro

AS/400

using RPG:

¹ overriding and redirecting file input and output

¹ file locking by an RPG program

¹ record locking by an RPG program

¹ sharing an open data path

¹ AS/400 spooling functions

¹using SRTSEQ/ALTSEQ in an RPG program versus a DDS file

Overriding and Redirecting File Input and Output

OS/400 commands can be used to description or to redirect a allows you to specify a file (at compilation time):

override a parameter in the specifie file at compilation time or run time. at run time to replace the file spe

Compile

Time

RPG program

File name = FILEY

Device = DISK

Execution

Time

FILEY

File type =

PHYSICAL

Override Command:

OVRDBF FILE (FILEY) TOFILE (FILEA)

FILEA

 

File type =

Diskette

DEVICE

 

Device type =

 

DISKETTE

 

Figure

136.

Overriding File Input and Output Example

 

 

 

 

In

the

preceding example,

the

CL

command

OVRDBF

(Override

With Datab

File) allows the program to

run

with an

entirely

different

device

fil

fied

at

compilation

time.

 

 

 

 

 

 

 

 

To

override

a file

at run

time,

you

must

make

sure that

record

nam

are the same. The RPG program uses the record-format name on the i operations, such as a READ operation where it specifies what record expected.

Not all file redirections or overrides are valid. At run time, checki specifications within the RPG program are valid for the file being OS/400 system allows some file redirections even if device specifics

Copyright IBM Corp. 1994, 1999

273

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IBM AS/400 manual File Considerations, Overriding and Redirecting File Input and Output, 273
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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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