Table 40. DOS PL/I Migration Considerations

Migration

Comments

Consideration

 

 

 

 

Dumps

The output produced by PLIDUMP is different when running

 

under OS/390 Language Environment.

 

 

Condition Handling

In general, PL/I condition handling continues to function in

 

the same way when running under OS/390 Language

 

Environment; however, you should consider the following:

 

The ERRCOUNT run-time option specifies how many

 

 

 

 

conditions of severity 2, 3, and 4 can occur before the

 

 

enclave terminates abnormally. The IBM-supplied

 

 

installation value for the ERRCOUNT run-time option is

 

 

ERRCOUNT(20). This value is not suitable for all PL/I

 

 

applications. To ensure that your application behaves

 

 

correctly, and is compatible with DOS PL/I behavior,

 

 

specify ERRCOUNT(0).

 

The diagnostic message for an ERROR condition is

 

 

 

 

issued only if there is no ERROR ON-unit established,

 

 

or if the ERROR ON-unit does not recover from the

 

 

condition by using a GOTO out of block. However, for

 

 

other PL/I conditions whose implicit action includes

 

 

printing a message and raising the ERROR condition,

 

 

the message is issued before control is given to an

 

 

established ERROR ON-unit.

 

 

Run-Time Message

OS/390 Language Environment directs run-time message

Output - SYSPRINT

output from PL/I programs to the file specified by the

 

OS/390 Language Environment MSGFILE run-time option,

 

instead of to the PL/I SYSPRINT file. User-specified output

 

is still directed to the PL/I SYSPRINT file. If you want

 

OS/390 Language Environment to handle this output,

 

specify the run-time option MSGFILE(SYSPRINT). When you

 

specify MSGFILE(SYSPRINT), SYSPRINT contains both

 

run-time messages and user-specified output.

 

 

Format and Content

The format and content of run-time messages is different

of Messages in PL/I

for PL/I applications running with OS/390 Language

 

Environment. If you have applications that analyze run-time

 

output, you should change them. Differences include:

 

The message number in the message prefix is now four

 

 

 

 

digits instead of three digits.

 

The message severity in the message prefix can now

 

 

 

 

be I, W, E, S, or C.

 

The message text of some mixed-case English and

 

 

 

 

Japanese messages has been enhanced.

 

 

DEPTHCONDLMT

The default setting for the DEPTHCONDLMT option, both for

Option

CICS and non-CICS, is DEPTHCONDLMT(10). The

 

recommended setting for PL/I applications, for compatibility

 

with DOS PL/I, is DEPTHCONDLMT(0).

 

 

Storage Report

The format of the run-time storage report generated by the

 

OS/390 Language Environment RPTSTG run-time option is

 

different than the format of the storage reports produced

 

by the DOS PL/I REPORT run-time option.

 

 

 

Chapter 17. Language Environment (LE) 357

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IBM OS/390 manual DOS PL/I Migration Considerations, Migration Comments Consideration, Depthcondlmt

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.