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Wipro Mainframe: What Command is Used to Control Assignments and Configuration of I/O Devices in Mainframe Systems?

By: Author Alex Lim

Posted on  - Last updated:

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Learn about the VARY command in mainframe systems and how it is used to control the assignment and configuration of I/O devices. Get a detailed explanation of this important z/OS operator command.

Table of Contents

Question

The _ command is used to control assignments and configuration of I/O devices

A. Vary
B. Switch
C. Swap
D. Start

Answer

A. Vary

Explanation

The VARY command is used in mainframe systems like IBM z/OS to control the assignment and configuration of input/output (I/O) devices.

Some key things to know about the VARY command:

  • It allows the system operator to change the online/offline status of I/O devices like disk drives, tape drives, printers, etc. Taking a device offline makes it unavailable for allocation to jobs and tasks.
  • VARY can be used to assign I/O devices to specific logical partitions (LPARs) in the mainframe environment. This controls which operating system images have access to which I/O resources.
  • The command can dynamically modify certain I/O device parameters and path configurations without requiring an IPL (system restart). This provides flexibility.
  • Some common uses include varying a device online or offline, assigning devices to LPARs, and controlling channel path accessibility.
  • The basic syntax is VARY ONLINE/OFFLINE, device name or VARY device name,ONLINE/OFFLINE.

So in summary, the VARY command is an essential tool for mainframe operators and administrators to manage the complex I/O configurations in Z Systems. It provides the ability to dynamically reconfigure I/O without disruption.

The other options listed – SWITCH, SWAP, START – are not correct in this context. SWITCH and SWAP have different meanings and START is used to initiate an I/O device or channel path that is already online, not to change its configuration.

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