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MVS DASD User Allocation Determination Method

IP.com Disclosure Number: IPCOM000051621D
Original Publication Date: 1981-Feb-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Ogden, WR: AUTHOR

Abstract

An MVS (multiple virtual storage) system operator sometimes needs to determine which TSO (time sharing option) users (or batch jobs) have a given DASD (direct access storage device) unit allocated. This situation usually occurs when the operator wishes to vary the unit OFFLINE; he cannot do this if any user(s) have the DASD allocated. There is no standard MVS facility to determine exactly which users (or jobs) have a given DASD unit allocated.

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MVS DASD User Allocation Determination Method

An MVS (multiple virtual storage) system operator sometimes needs to determine which TSO (time sharing option) users (or batch jobs) have a given DASD (direct access storage device) unit allocated. This situation usually occurs when the operator wishes to vary the unit OFFLINE; he cannot do this if any user(s) have the DASD allocated. There is no standard MVS facility to determine exactly which users (or jobs) have a given DASD unit allocated.

A program having the following logic can provide the operator (or authorized TSO user) with a list of all users and jobs having a given DASD unit allocated. The input to this routine is the unit address; the output is a variable length list containing the user/job name and the DD name of the dataset(s) allocated to the unit. The exact coding of this program is not critical and is not listed. Assuming that a number of common service subroutines are available, the following "mainline" routine requires a relatively small amount of assembler code.

The method is as follows:
1. Obtain and scan the 3-byte device name operand.
2. Attempt to look up the corresponding UCB (unit control

block) to verify that it exists and is online.
3. Scan the ASVT to locate every active address space.
4. Obtain the ASCB address from the ASVT; obtain the user/

job name via ASCB pointers.
5. Schedule a special SRB (system request block) routine into

the address space, passing the specified UCB address as a

parameter.
6. When the SRB routine completes, use the data re...