In OS/390 the DATE function can be replaced by a control card, a parameter on the EXEC statement, or a date simulation tool.

4.3.9.2 UPSI

The UPSI switches that were on the 1401s got a second life in DOS with the System/360. UPSI can be tested in RPG, Assembler and in COBOL. For more information on the manipulation of UPSI with Assembler see Chapter 13, ªAssemblerº on page267. In OS/390, COBOL and RPG support UPSI through the PARM= on the EXEC statement. There is no support for UPSI in Assembler or PL/I. A feature of VSE UPSI statements is that they are carried over from one step to the next until the end of the job.

Many VSE utility programs that use UPSI have an equivalent in MVS which, obviously, does not use UPSI. For this reason, it is frequent that a large number of UPSI cards in the VSE JCL do not need to be converted to MVS.

The VSE application can modify the value of the UPSI byte internally using the MVCOM macro. This can be identified by inspecting the MVCOM macros in Assembler subroutines.

4.3.10 VSE Job Control Statements

4.3.10.1 Job Statement

The job statement is mandatory in OS/390 (it could be omitted in VSE; some say this makes it optional). Many times the VSE job card may be used to delineate a step (that is, if there is only one EXEC statement in the VSE job being converted).

Accounting information from the VSE job card may be specified in the MVS JOB or EXEC statement using the ACCT= keyword.

4.3.10.2 EXEC Statement

The EXEC statement in VSE is similar to MVSEXEC statement. It is used to identify the program or procedure to be executed. It also specifies storage SIZE requirements (similar to the MVS EXEC REGION parameter), and parameters to be passed to the program or procedure to be executed.

There are differences in defaults and parameter specifications. In VSE, the default for the name is a program module, while in MVS, the default is the name of a procedure. Thus, in VSE, you find

// EXEC PROC=procname,.. to execute a procedure

// EXEC IDCAMS,... to execute a program

// EXEC REXX=rexxproc,.. to execute a REXX procedure

while in MVS you would find

 

//STEPNAME EXEC procname,...

to execute a procedure

//STEPNAME EXEC PGM=IDCAMS,...

to execute a program

//STEPNAME EXEC PGM=IRXJCL...

to execute a REXX procedure

4.3.10.3 TLBL Statement

The TLBL in VSE is equivalent to the DD statement for a labeled tape file in OS/390 (an unlabeled tape does not need a TLBL). The VSE filename (the DTF name) which can be up to seven characters long, is equivalent to the MVS DDname, which can be up to eight characters long.

82VSE to OS/390 Migration Workbook

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IBM OS/390 manual VSE Job Control Statements, Upsi, Job Statement, Exec Statement, Tlbl Statement

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.