each application had its own 16mbyte virtual address space ... however possibly 13mbytes of each virtual address space was common ... leaving ... effectively at most 3mbytes unique for application.
lets say most of the mvs kernel (8mbytes) and most of a 5mbyte common segment was resident at a particular moment ... that would take up 13mbytes of real storage ... leaving possibly 19mbytes (out of 32mbyte real). you could have dozens of applications and subsystems running concurrently ... each with their own unique address space and unique pages. lets say there were 40 concurrent applications and subsystems that might be running at any point in time ... if they had the max. 3mbytes each ... that would account for 120mbytes of total unique virtual memory (spread across the 40 different virtual address spaces). whith possibly only 19mbytes left of available real storage ... only 19mbytes of the 120mbyte possible virtual pages could be resident in real storage at any point in time. Great example.If IBM readbooks have such detailed examples for beginners ...I know it's impossible,so I would thank you again for it. Maybe the last question I would like to raise is for the system common area. lets say most of the mvs kernel (8mbytes) and most of a 5mbyte common segment was resident at a particular moment ... that would take up 13mbytes of real storage Just as you said,because some of common area is pageable,it's not likely that all system area is resident in real storage at any time. Then,what about the size of shared system area in terms of virtual storage? I mean,is it fixed or variable? ABCs of z/os system programming vol-1 says: When modules are added to LPA, the growth in LPA can cause the common area to cross one or more segment boundaries, which reduces the available private area by a corresponding amount; each time the common area crosses a segment boundary, the available private area for all address spaces in the system is reduced by the size of one segment, even for those address spaces not using the load modules added to LPA So the common area size can becom bigger dynamically while system is running,which impacts all address space and causes the available private area of them decrease.However,if an address space has used up all of its available private area,will the force decrease of its private area cause problems?Say,you allocate a 100M region for a tso user and this user is executing a program in this address space which occupies all 100M virtual storage space.Then the common area increases.What happens to this user's address space and the program he is executing? -- 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
