Knowledge Management

Question:
Can any guru explain me or show me the way to understand the concept of extended memory .
and Does it come from physical memory or it comes from virtual memory
which is physical + swap .
does EM is limited by the physical memory meaning if my physical memory is 1 GB then does that imply that i can't keep extended memory more than 1 GB and it has to be within 1 GB or can i keep it more if my virtual memory is 4 GB ( physical + swap )
Thanks in advance
Answer:
Operating system will not reject the SAP's request of EM more than available RAM installed. The concept goes back to Mainframess, where there is no difference between RAM and SWAP space
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