Bruce writes:
>Stan Sieler writes:

>>   So...we said, hey...let's just do:
>>           build foo; rec=128,1,f,binary; disc=1024,2,2
>>   this builds a file of 1024 * 256 bytes, fully allocated on disk,
>>   whose EOF is 0 and whose LIMIT is 1024.
>>   Then, we HPFOPEN it (with long mapped access) and use it.

>I have a number of scars to show for using this approach.

ORBiT has as well. We discovered way back when (and to be sure, I'm not
sure this is still the case), that when writing to pages beyond the EOF
in a high memory pressure situation, the OS reused the real memory that
those pages were mapped into without preserving the old pages. I think
that Jerry Fochtman has seen something similar more recently (Jerry -
wanna speak up?) that is simliar.

Now I know this isn't exactly what Stan's doing as he's counting on
this not being durable, whereas ORBiT was doing the opposite. I just
want to point out that this technique is ripe with "gotchas".

This still doesn't answer the direct XLTRIM question, but for once,
I have no opinion on that. :-)