When a program is selected for execution, the system brings it into virtual storage, divides it into pages of four kilobytes, transfers the pages into central storage for execution. To the programmer, the entire program appears to occupy contiguous space in storage at all times. Actually, not all pages of a program are necessarily in central storage, and the pages that are in central storage do not necessarily occupy contiguous space.
The pieces of a program executing in virtual storage must be moved between real and auxiliary storage. To allow this, z/OS® manages storage in units, or blocks, of four kilobytes. The following blocks are defined:
* A block of central storage is a frame.
* A block of virtual storage is a page.
* A block of auxiliary storage is a slot.
A page, a frame, and a slot are all the same size: Four kilobytes. An active virtual storage page resides in a central storage frame. A virtual storage page that becomes inactive resides in an auxiliary storage slot (in a paging data set). Figure 1 shows the relationship of pages, frames, and slots.
Answered by
jaivir
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10:05 AM on September 04, 2008