Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Virtual Tasking

IP.com Disclosure Number: IPCOM000079268D
Original Publication Date: 1973-Jun-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Boggs, JK: AUTHOR

Abstract

Virtual tasking combines the advantages of Overlay, Paging, and Tasking into one system facility. A) Virtual Tasking Description This facility provides for: (1) Independent, swapped tasks with their own unreused address space. (2) No quiesce of I/O during swap. (3) Full facilities of OS/VS-1 task. (4) Time slicing of partition time among virtual tasks. (5) During I/O, which is left outstanding while task is swapped, the I/O areas remain with PP protect key out not referenceable through active segment table. Tasking Mechanism (1) Task control blocks maintained in partition (Protectable Queue Area) PQA.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 97% of the total text.

Page 1 of 1

Virtual Tasking

Virtual tasking combines the advantages of Overlay, Paging, and Tasking into one system facility. A) Virtual Tasking Description

This facility provides for:

(1) Independent, swapped tasks with their own unreused

address space.

(2) No quiesce of I/O during swap.

(3) Full facilities of OS/VS-1 task.

(4) Time slicing of partition time among virtual tasks.

(5) During I/O, which is left outstanding while task is

swapped, the I/O areas remain with PP protect key out

not referenceable through active segment table.

Tasking Mechanism

(1) Task control blocks maintained in partition (Protectable

Queue Area) PQA.

(2) Partition "cut up" into subpartitions based upon number

of virtual tasks and size of each (specified on an

ATTACH main instruction).

(3) Subtasks of virtual tasks are valid: their TCB's are

allocated in virtual tasks PQA.

(4) Boundary box for virtual task and segment table are

contained in partition PQA.

Relocate Mechanism

(1) Virtual task PQA is swapped along with program space.

(2) Segment table for virtual task is referenced by IOS

to temporarily reinstate virtual task for out of core

post condition. (this causes temporary suspension

of current virtual task).

(3) System task dispatcher recognizes virtual task switch

and exchanges segment tables to make addressable newly

activated virtual task.

(4) Addressability of partition task areas remains

addressable by and unprotected from all virtual tasks.

(5) Upon virtual task switch, place all pages...