Methods for Processing Disk Files

Limits Records

For sequential-within-limits processing, the record-address file contains

records.

A limits record

contains

the lowest

record key

and the hig

of

the

records

in

the

file

to

be

read.

 

 

The

format

of the

limits

records in the record-address file is as

¹

The

low

key

begins in

position

1

of the

record; the high key i

 

the

low

key.

No

blanks

can

appear

between

the keys.

 

¹Each record in the record-address file can contain only one set

record length must be greater than

or

equal

to

twice

the

length

key.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

¹ The

low

key and

the

high

key in

the

limits

record

must

be

the

The

length of the

keys must

be

equal

to the length

of

the

key

be

processed.

 

 

 

 

 

 

 

 

 

 

 

 

 

¹ A blank entry equal

in

length

to

the

record

key

field

causes the

piler to

read

the

next

record

in

the

record-address

file.

 

Relative Record Numbers

For relative-record-number processing, the record-address file contains record numbers. Each record retrieved from the file being processe relative record number in the record-address file. A record-address relative record numbers cannot be used for limits processing. Each re number in the record-address file is a multi-byte binary field wher tains a relative record number.

You

can

specify

the

record-address file length

as

4,

3,

or

blank,

source

of

the

file.

When using a

record-address

file

from the

AS/4

specify

the

record-address file length as 4,

since

each

field

is

When

using

a

record-address file created for

the System/36,specifyEnvironment

the record-address file length as 3, since each field is

3

bytes

specify

the record-address file length as blank,

the compiler

will

c

record

length

at

run time and determine whether

to

treat

the

recor

3

byte

or as

4

byte.

 

 

 

 

 

 

 

 

 

A

minus

1

(-1

 

or

hexadecimal

FFFFFFFF)

relative-record-number

value

stops

use

of

a relative-record-address file record.

End

of

file

occurs w

the

record-address file have

been

processed.

 

 

 

 

 

 

 

Methods for Processing Disk Files

The methods of disk file processing include:

¹Consecutive processing

¹Sequential-by-key processing

¹Random-by-key processing

¹Sequential-within-limits processing.

¹Relative-record-number processing

Chapter 16. Accessing Database 291Files

Page 314 Page 316
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IBM AS/400 manual Methods for Processing Disk Files, Limits Records, Relative Record Numbers
Page 314 Page 316

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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