(MVS)

LOAD

EP=PROGB

LOAD the load-module

LR

15,0

pass address

CALL

(15),parm1,parm2

invoke PROGB

FETCH Macro

The VSE FETCH macro loads the phase specified in the first parameter and passes control to the address specified by the second. The MVS LINK and XCTL macros pass control to a specified entry point. When modifying programs from VSE to MVS, use LINK when the called phase does not overlay the calling phase. Use XCTL when the called phase does overlay the calling phase. When using XCTL, ensure that all DCBs and ACBs in the calling programs have been closed prior to issuing XCTL.

CDLOAD and CDDELETE Macros

The MVS LOAD and DELETE macros have functions similar to the VSE CDLOAD and CDDELETE macros. The CDLOAD macro can be used repetitively against the same module, first to load it, then to retrieve its address. In this case, to achieve the same result in MVS with the LOAD macro, the loaded module must be link-edited with the REUS attribute.

Example:

 

 

(VSE)

 

 

LA

1,PHASENM

address of the phase name

CDLOAD (1)

LOAD the phase

LR

15,1

pass address

CALL

(15),parm1,parm2

invoke PROGB

(MVS)

 

 

LOAD

EPLOC=PHASENM

LOAD the load-module

LR

15,0

pass address

CALL

(15),parm1,parm2

invoke PROGB

WTO and WTOR Macros

The MVS WTO and WTOR macros have functions similar to the VSE/ESA WTO and WTOR macros.

GETIME Macro

The VSE GETIME macro provides the time of day, (local or Greenwich Mean Time) based on a 24-hour clock, in register 1 in a form dependent upon the operand(s).

The MVS TIME macro has the same basic function as the VSE GETIME LOCAL macro. The main differences between the two macros is in register usage and degree of precision (Figure 30 on page 279). For the DEC, BIN, and TU operands, the TIME macro returns the time in register 0 and the Julian date in register 1. The date is returned in register 1 as packed decimal digits in the form 0C YY DD DF, where 0C is the century indicator, YY is the last two digits of the year, DDD is the day of the year and F is a sign character that allows the date to be unpacked and printed. If the date is needed as day/month or month/day, you must provide a routine to convert the data.

278VSE to OS/390 Migration Workbook

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Image 302
IBM OS/390 manual Ep=Progb, VSE Phasenm, Cdload, Eploc=Phasenm

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.