Johnny, Comments below: Wayne Driscoll Product Developer JME Software LLC NOTE: All opinions are strictly my own.
-----Original Message----- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of Johnny Luo Sent: Friday, February 10, 2006 9:41 AM To: [email protected] Subject: Multiple address spaces Hi, MVS(Multiple Virtual Storage) is the basic concept for z/os.However,after entering the mainframe world for eight months I still cannot understand it thoroughly，especially for ' multiple address spaces'. To make things simple,I'll assume 31-bit addressing only. 1,MVS allow different task to have their own address space.While the number of address space increases in system,the total amount of virtual storage can become very big. However,as I know,virtual storage is supported by real storage and auxiliary storage.With 31-bit addressing,the max size of real storage or auxiliary storage is 2G. So,the max size of virtual storage=max real storage+max auxiliary storage=4G WD - NO - The paging system is only limited by the maximum size of a page dataset times the maximum number of page datasets. Does this mean that the total size of all the address spaces cannot exceed 4G although in theory each address space can have a max size of 2G? WD - No see above. 2,Take a TSO user's address space for example.Suppose its size is 5M.Whenthe user logon to tso,the address space is established which means 5M virtual storage space is allocated for this address space.So this 5M space is being mapped using real storage plus auxiliary storage even if the user doesn't do any job after logon? WD - No, When a user logs on with a REGION of 5M (small, but for demonstration purposes, ok). The 5M is the MAX region allowd, but virtual storage isn't actually mapped until the page has been allocated by a program in that address space. -- Best Regards, Johnny Luo ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
