28.3.3 Stopping the System

There are several ways to stop or halt the system, and important subsystems. Here is a simple example of commands to stop the system:

$Pxxx

Drain all active JES2 printers, initiators and so on

P TSO

Stop Time-sharing

Z NET,QUICK

Stop VTAM

C APPC

Stop APPC (if active)

D A,L

Display active jobs to see what else needs to be stopped

P RMF

Stop RMF (and any other active subsystems)

$PJES2

Stop JES2 (see options below)

Z EOD

Flush all SMF buffers, LOGREC, Caches and so on to external

 

DASD

Now you can safely power the processor off or re-IPL.

Stopping JES2

There are various flavors of the $PJES2 (stop JES2) command:

$P JES2

Stop JES2 after ²all available functions are complete.² This

 

usually takes forever to drain all the devices, processes, jobs

 

and started tasks, that were started under JES.

$P JES2,TERM

This is quick and the recommended way to stop JES2 if you

 

know you are going to re-IPL.

$P JES2,ABEND

Stop JES2 immediately so you can ²hot-start² it without an

 

intervening IPL.

28.4 Controlling Devices

Some devices such as the system volumes or work packs are permanently resident, always mounted, and shared amongst users. Devices such as tape drives are allocated to one job at a time as they are needed. Others, like printers are managed by JES2 so they can be used by all jobs.

28.4.1 Displaying the Status of Devices

Use the ²D U² command to see the status of various devices by device address or device type. For example, enter ²D U,DASD,ONLINE² to display online DASD units and their volume serial numbers.

Use the ²D M² command to see the paths to devices.

28.4.2 Understanding Device Allocation

Batch jobs and other users allocate devices for their work, and operators may be prompted to mount or otherwise respond to these requests.

See section 1.8 ²Interacting with System Functions² in MVS Commands for a description of Device allocation, Hot I/O detection, and Device ²boxing². Section 1.9 describes the SWAP command to respond to Failing Devices.

448VSE to OS/390 Migration Workbook

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IBM OS/390 Stopping the System, Controlling Devices, Displaying the Status of Devices, Understanding Device Allocation

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.