Spool Interface restrictions

∙RPG II is not a supported language for CICS/OS. RPG II programs should be converted to a supported application language (that is, COBOL, PL/I, C++, and or Assembler).

∙Programs that directly invoke operating system services.

∙Programs that directly access operating system control blocks.

∙Programs that access internal CICS control blocks (DSECTs).

∙The CICS/VSE Report Controller Feature (RCF) is not supported by CICS/MVS. This includes many suboperands of the EXEC CICS SPOOL commands. The basic spool interface (open, close, read, and write) functions are available in both CICS/VSE and CICS/MVS.

∙The CICS provided programming interface to JES (the Job Entry Subsystem component of MVS) allows CICS applications to create and retrieve spool files. Spool files are managed by JES and are used to buffer output directed to low-speed peripheral devices (printers, punches, and plotters) between the job that creates them and actual processing by the device. Input files from card readers are also spool files and serve as buffers between the device and the jobs that use the data.

The interface consists of five commands:

SPOOLOPEN INPUT, which opens a file for input SPOOLOPEN OUTPUT, which opens a file for output SPOOLREAD, which retrieves the next record from an input file SPOOLWRITE, which adds one record to an output file SPOOLCLOSE, which closes the file and releases it for subsequent processing by JES.

There are internal limits in JES that you should consider when you are designing applications. Some apply to JES2, some to JES3 and some to both. In particular:

JES2 imposes an upper limit on the total number of spool files that a single job (such as CICS) can create. If CICS exceeds this limit during its execution, subsequent SPOOLOPEN OUTPUT commands fail with the error condition.

JES3 does not impose such a limit explicitly, but for both JES2 and JES3, some control information for each file created persists for the entire execution of CICS. For this reason, creating very large numbers of spool files can stress JES resources.

Spool files require other resources (buffers, queue elements, disk space) until they are processed. Please review the CICS Application Programming Guide for more details.

However, spool read is single thread in CICS/MVS. This may have significant performance implications. Similar functions may be provided in the MVS environment by the Report Management and Distribution System (RMDS), 5665-310.

∙If your CICS applications have exploited the menu services provided by the VSE Interactive Interface (II) they may need some rework. The II selection panels and II programs such as IESFPIP do not exist in CICS/ESA. The functions may be provided by user written CICS programs and maps. Similar

Chapter 6. CICS 151

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.

IBM OS/390 manual Spool Interface restrictions

Models: OS/390