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icemanster
New User
Joined: 30 Jan 2009
Posts: 8
Location: Manila
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Hi i would just like to ask when do we use ADDRSPC=REAL
i saw this from the net:
ADDRSPC: this parameter specifies whether your job should use the Virtual memory or the Real memory when executing.
Advantage of Virtual memory is , the Job can be paged. Virtual is Default.
Region:- Region parameter allocates the specified memory in the Real storage or Virtual storage as mentioned in the ADDRSPC parameter.
If they are coded in the EXEC statement , then they are applicable only for that step.
If coded both on job and exec then Job overrides Exec.
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here is my question..
1. what is paged?
2. what happens when REAL is used? I believe real means central storage.. what is central storage?
I hope you could help me with this one.. Thank you very much! |
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Robert Sample
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Joined: 06 Jun 2008
Posts: 8696
Location: Dubuque, Iowa, USA
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1. Memory is paged (if needed). This means if another job needs more memory, and your job can be paged, your memory can be written to auxiliary storage and the memory pages taken over by the other job. This is basic virtual systems -- if you're running on an IBM mainframe and don't know this you could have lots of future problems.
2. REAL means non-pageable memory is used -- which is typically reserved for use by the operating system, pretty much never is needed by applications programmers, and also tends to be quite limited. Started tasks, utilities, and operating system components typically are the only programs using REAL memory. |
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Anuj Dhawan
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Joined: 22 Apr 2006
Posts: 6250
Location: Mumbai, India
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| You might compare these concepts with "RAM" & "ROM". Real memory refers to the actual memory chips that are installed in the computer. All programs actually run in this physical memory. However, it is often useful to allow the computer to think that it has memory that isn't actually there, in order to permit the use of programs that are larger than will physically fit in memory, or to allow multitasking (multiple programs running at once). This concept is called virtual memory. |
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Anuj Dhawan
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Location: Mumbai, India
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icemanster
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Joined: 30 Jan 2009
Posts: 8
Location: Manila
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| Thanks for the much needed info guys! |
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Anuj Dhawan
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Joined: 22 Apr 2006
Posts: 6250
Location: Mumbai, India
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Glad to help you... |
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