JdBP>   do, it gains nothing, because eliminating buffer

Actually,  it gains access to functions that take a "char *"
instead of a "FILE *" (or other stream).

 JdBP>   Scenario B, partial file mapping using a window :

 JdBP>      Client asks for pointer to record N.
 JdBP>      DB library checks that N is within partial mapping "window".

This would happen in the exception handler;  it would never have to check
-- and excpetion would be rasied if it wasn't.

 JdBP>   For a real world implementation of partial file mapping, there's also
 JdBP>   the headache of what to do when the client wants 
 JdBP> to access two records
 JdBP>   separated by a distance greater than that of the window size.

There is no reason why you have to use a "window".  You can
simply cache the last 'n' 4k pages, and as someone else suggested,  use LRU
on them.


--- Maximus/2 2.01