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What is the use of specifying the ADDRSPC as REAL or VIRTUAL

 
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sureshmurali
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Joined: 25 Nov 2010
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Location: Sivakasi, India

PostPosted: Tue Dec 21, 2010 9:00 pm    Post subject: What is the use of specifying the ADDRSPC as REAL or VIRTUAL
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Hi

I already studied about memory paging concepts.
Virtual Memory - When a program of huge size needs to be executed and if the memory is not able to fit to hold that program, then a portion of the secondary storage device would be allocated and the program will be stored as pages. Whenever the main memory needs a particular page to execute it, page replacement takes place between main and secondary memory and in this way the execution takes place.

I also studied that the OS programs, utilities and start up programs usually requires REAL ADDRSPC.

My Question here is what is the benefit will i have if i set the ADDRSPC of a job as REAL? Lets take a case...If i set the ADDRSPC as REAL for my job and if there is no space in the main memory for the next program which has high priority and its ADDRSPC is REAL, what the system will do that time?

Please explain the advantages and disadvantages of both ADDRSPC. because i could understand what are they? But couldnt understand the benefit of their usage?

Thanks in advance.

Suresh K
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Pedro

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Joined: 01 Sep 2006
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Location: Silicon Valley

PostPosted: Tue Dec 21, 2010 9:14 pm    Post subject: Reply to: What is the use of specifying the ADDRSPC as REAL
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Quote:
utilities and start up programs usually requires REAL ADDRSPC

I do not believe this to be true. Please cite your reference.

I have never used that parm in 30 years, so I do not think you need to use it nor even know about it.
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sureshmurali
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PostPosted: Tue Dec 21, 2010 10:44 pm    Post subject:
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Hi
Sorry. I was supposed to post this under JCL forum. Please excuse.
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dick scherrer

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PostPosted: Tue Dec 21, 2010 11:20 pm    Post subject:
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Hello,

Why do you believe this is a JCL question/topic?

The duplicate topic has been deleted as this one already has dialog.

If there is some reason to relocate this, just post a reply and it can be moved.
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don.leahy

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Location: Whitby, ON, Canada

PostPosted: Tue Dec 21, 2010 11:49 pm    Post subject:
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I have never used ADDRSPC in my 29 years in this business, but 5 minutes of Googling was enough to convince me that this is something that the application programmer should not mess with. To do so might provoke the wrath of your local sysprogs.
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Robert Sample

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Joined: 06 Jun 2008
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Location: East Dubuque, Illinois, USA

PostPosted: Wed Dec 22, 2010 6:24 am    Post subject:
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ADDRSPC=REAL is used when a program cannot be paged, usually due to timing issues. For example, the TCP/IP programs such as FTP require some real memory since there are time-dependent functions that could be impacted if memory paging occurred.

If a program requires ADDRSPC=REAL, that will be clearly noted in the installation instructions. No application programmer should ever use this parameter -- using it incorrectly could impact the entire LPAR workload (batch jobs, TSO sessions, started tasks, CICS regions, DB2 -- everything).

Contact your site support group if you feel you need this option -- they can provide you the site rules on using it (and the penalties for using it without permission).
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sureshmurali
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PostPosted: Wed Dec 22, 2010 8:18 am    Post subject:
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Hi friends,

Thanks for your reply.
I was eager to know the usage of REAL ADDRSPC.
Robert With your kind answer, i understood the thing.
Thanks a lot.
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