RE: Laymans explaination for single level store?

>A simple, familiar example for this process is using a word
processor...
>An alternative approach is to have only one copy of the file...

And how would you handle close w/OUT save? You can simply map your word
processor document into memory on Windows today, any update to a
"memory" location IS an update in the file on the disk, effectively it's
only in one spot -- an no, it will NOT be in the swap file. (See
CreateFileMapping API)

However, if you did that, how would you close your word processing
document w/OUT saving changes? The changes have already made their way
to disk, IN the original document. The main reason you map documents
into memory today isn't because we can't edit them on disk, we can, it's
for performance or operational reasons, like having the ability to
discard changes.

>"The open and close operations no longer must physically copy the
entire
>file from its permanent location on the disk.  Only the portion (or
record)
>you're reading or working on is copied to a memory buffer.  We often
>describe this by saying files are always used "in place," thereby
improving
>overall system performance."

OK, clearly that's not a requirement of Windows. How do you think
SQLServer handles multi-terabyte databases? By reading the entire thing
into virtual-memory, hah!

-Walden

------------
Walden H Leverich III
President & CEO
Tech Software
(516) 627-3800 x11
WaldenL@xxxxxxxxxxxxxxx
http://www.TechSoftInc.com 

Quiquid latine dictum sit altum viditur.
(Whatever is said in Latin seems profound.)