.

 

Notes

 

 

 

 

OPEN

(R0FILE,(OUTPUT),TAPE)

 

WRITER0

WRITE

DECBR0,SZ,R0FILE

 

 

STC

15,RC

(1)

 

CHECK

DECBR0

 

 

CLI

RC,X′ 0 0 ′

 

 

BE

WRITER0

(2)

OPENDAM

OPEN

(DAMFILE,(OUTPUT))

 

 

CLI

WC,X′ 1 0 ′

(3,8)

 

BE

WRITE

 

GET

GET

TAPE,WORK

 

 

PACK

PKEY(2),KEY

 

 

CVB

9,CVBKEY

 

 

SR

8,8

(4)

 

D

8,=F′ 3 7 ′

 

 

LTR

8,8

 

 

BNZ

*+10

 

 

BCTR

9,0

 

 

IC

8,=C′ 3 7 ′

 

 

STH

9,TT

 

 

STC

8,R

 

WRITE

WRITE DECBLOAD,DAF,DAMFILE,DATA,47,KEY,TTR (5)

 

WAIT

ECB=DECBLOAD

 

 

MVC

WC,DECBLOAD+2

 

 

TM

WC,X′ 1 O′

(6)

 

BO

CLOSEDAM

(7)

CHECK DECBLOAD

BGET

CLOSEDA AH 7,COUNT LA 7,0(7) STH 7,COUNT CH 7,THREE

BH BYPASS CLOSE (DAMFILE)

BWRITER0

BYPASS

NOTE

RECORD

 

B

GET

EOF

CLOSE (DAMFILE)

 

CLOSE (R0FILE,,TAPE)

 

.

 

WORK

DS

0CL50

KEY

DS

CL3

DATA

DS

CL47

 

DS

CL30

CVBKEY

DC

D′ 0 ′

PKEY

EQU

*-2

TTR

DS

0F

TT

DS

CL2

R

DS

CL1

*

DS

CL5

 

 

 

 

 

Figure 49

(Part 1

of 3). Loading a DAM File of U. or V. Length Records under MVS

Chapter 13. A s s e m b l e r 321

Page 344 Page 346
Page 345
Image 345
IBM OS/390 manual Open R0FILE,OUTPUT,TAPE WRITER0, DECBR0,SZ,R0FILE STC, DECBR0 CLI, Open DAMFILE,OUTPUT CLI, Ltr Bnz, Bctr
Page 344 Page 346

OS/390 specifications

IBM OS/390, a versatile operating system, was a cornerstone in enterprise environments and played a pivotal role in mainframe computing. Released in the mid-1990s, OS/390 combined the strengths of IBM's MVS (Multiple Virtual Storage) with new features and enhancements, targeting scalability, reliability, and performance in demanding business applications.

One of the key features of OS/390 was its robust support for multiple users and processes. The system allowed thousands of concurrent users to access applications and data, ensuring high availability and minimizing downtime—a critical requirement for many large organizations. This scalability was supported through various enhancements in memory management and processor scheduling, enabling optimal resource allocation across diverse workloads.

OS/390 was known for its superior workload management capabilities. The Workload Manager (WLM) component allowed administrators to define service policies, specifying how system resources would be allocated according to the priority of tasks. This ensured that critical business processes received the necessary resources while less critical tasks were managed more flexibly.

Another significant characteristic of OS/390 was its commitment to security. The operating system provided comprehensive security features, including user authentication, data encryption, and auditing capabilities. This focus on security was vital for organizations handling sensitive data, ensuring compliance with regulations and safeguarding against unauthorized access.

OS/390 also supported advanced technologies that facilitated integration and development. The system included features like the IBM CICS (Customer Information Control System) for transaction processing and IMS (Information Management System) for database management. These technologies allowed organizations to build robust, high-performance applications tailored to specific business needs.

The ease of network integration was another strength of OS/390. With the advent of the Internet and global connectivity, OS/390 systems could easily interface with various network protocols, enabling businesses to operate in a connected world. This inclusion paved the way for many organizations to expand their capabilities and offer new services, driving digital transformation.

In conclusion, IBM OS/390 represented a significant advancement in mainframe technology, combining scalability, security, and robust workload management. Its rich feature set and support for critical enterprise applications solidified its role as a vital component of many organizations' IT infrastructures, ensuring they could meet their operational challenges head-on while supporting future growth. As technology continues to evolve, the legacy of OS/390 remains influential in the realm of computing.
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