VSE CALL

Entrypoint ,(PARAMETER LIST)

 

(15)

 

MVS CALL

Entrypoint ,(ADDRESS),VL

 

(15)

,ID=number

Call is used the same way in MVS as it is in VSE, except when it is used with the LOAD macro. For a discussion of this difference, see the topic ªLOAD Macroº on page 277 in this section. In addition, if a variable number of parameters may be passed, the VL keyword operand must be added. The parameters of the called module should be checked for VSE and MVS differences. If differences are found, make the necessary changes. See the following example.

VSE

 

 

MVS

CALL SUBRTN1

 

CALL SUBRTN1

CALL SUBRIN2,(TAB,BK)

CALL SUBRTN2,(TAB,BK),VL

VSE SAVE

(r1

,r2)

 

MVS SAVE

(regl ,reg2)

,T ,identifier name

Under MVS, the SAVE macro causes the contents of the specified registers to be stored in the save area at the address contained in register 13 (within the calling program). Use the SAVE, macro only at the entry point of a program. Do not use the SAVE macro in a program interruption exit routine. When you use the T and identifier name parameters, the code resulting from the macro expansion requires that register 15 contain the address of the SAVE macro.

The T operand specifies that registers 14 and 15 are to be stored in words 3 and 5 of the save area. It thus permits you to save two noncontiguous sets of registers. The identifier name operand is an identifier that aids in locating a programs save area in a dump. It can be a complex name of up to 70 characters. Coding an identifier name causes the SAVE macro expansion to include:

A count byte containing the number of characters in the identifier name. This byte is assembled four bytes following the address contained in register 15.

The character string containing the identifier name. This string is assembled following the count byte.

An instruction to branch around the count and identifier name fields.

Sample MVS SAVE:

 

 

 

LAREX

CSECT

 

 

 

 

 

USING

*,11

Establish Addressability

 

 

LA

15,SAVEIT

Address of SAVE macro

SAVEIT

SAVE

(14,12),,*

 

+SAVEIT

B

10(8,15)

Branch around ID

+

 

DC

AL1(6)

 

+

 

DC

CL6′ SAVEIT′

Identifier

+

 

STM

14,12,12(13)

Save registers

 

 

 

 

 

 

VSE

 

RETURN

 

(r1,r2)

 

 

 

 

 

 

MVS

 

RETURN

 

(reg1 ,reg2) ,T ,RC = number

 

 

 

 

 

,RC =(15)

 

 

 

 

 

 

272VSE to OS/390 Migration Workbook

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Image 296
IBM OS/390 VSE Call, MVS Call, Call SUBRTN1, Call SUBRIN2,TAB,BK, Larex Csect Using, 15,SAVEIT, +Saveit, CL6′ SAVEIT′

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.