IBM Mainframe Forum Index
 
Log In
 
IBM Mainframe Forum Index Mainframe: Search IBM Mainframe Forum: FAQ Register
 

What is an address space? is it a logical existence


IBM Mainframe Forums -> JCL & VSAM
Post new topic   Reply to topic
View previous topic :: View next topic  
Author Message
ammu

New User


Joined: 10 Jun 2004
Posts: 3
Location: chennai

PostPosted: Thu Jun 10, 2004 4:52 pm
Reply with quote

what is an address space? is it a logical existence?
Back to top
View user's profile Send private message
mmwife

Super Moderator


Joined: 30 May 2003
Posts: 1592

PostPosted: Mon Jun 14, 2004 2:24 am
Reply with quote

Hi Ammu,

As I recall the concept of an address space arrived with the advent of virtual memory. At least that's when I first became aware of the term.

Since the internal "main" memory required by a pgm no longer corresponded to its size the term "address space" was coined to identify the space required bt the progam.

Although the "main" memory required by a pgm is now a fraction of its load module size it still is assigned a region that reflects the overall size of the pgm.

This region now exists on DASD (virtual storage) rather than real (main) memory and the segments of the pgm are paged in to real memory. The number of pages present in real memory at any given moment is called the working set.

Well, that's what I recall. There may be (most likely) some minor misstatements and omissions, but it should give you a ppretty good overview of the concept.

Regards, Jack.
Back to top
View user's profile Send private message
imvs

New User


Joined: 12 May 2004
Posts: 33

PostPosted: Mon Jun 14, 2004 11:06 am
Reply with quote

Address Spaces

An address space is the amount of virtual storage seen by a job

MB in MVS/SP and older systems
GB in MVS/XA and MVS/ESA
Each job executes in an address space
Online users each have a Time Sharing User (TSU) address space
Batch jobs execute in an Initiator address space
An address space is organized as a set of:
Segments (1MB each)
Pages (256 pages per segment, each page is 4K)
An address space is either:
Swapped out (all segments are on auxiliary storage)
Swapped in (at least one segment is in real storage)
Back to top
View user's profile Send private message
View previous topic :: :: View next topic  
Post new topic   Reply to topic View Bookmarks
All times are GMT + 6 Hours
Forum Index -> JCL & VSAM

 


Similar Topics
Topic Forum Replies
No new posts Replace each space in cobol string wi... COBOL Programming 3
No new posts Routing command Address SDSF to other... TSO/ISPF 2
No new posts Rotate partition-logical & physic... DB2 0
No new posts Merge 2 lines based on Space from a S... DFSORT/ICETOOL 5
No new posts Allocated space calculation from DCOL... PL/I & Assembler 3
Search our Forums:

Back to Top