Re: Memory Allocation Question

[Scott Klement <rpg400-l@xxxxxxxxxxxxxxxx>]

Hi Tony,

> will be run monthly, I am considering another strategy, using memory.
> I know that I can allocate memory, base a pointer on that memory, and
> do the same thing I was doing to the user space to actual memory.  My
> question is, what is the limit, and is there one.  What happens if I
> end up alloc'ing ~10Meg?  Does this seem like a reasonable strategy?
> Will it be faster?

Assuming that you're using %alloc() or the ALLOC op-code to allocate the
memory, the limit is about the same as that of a user spac. 16mb! If you
choose to use teraspace allocations instead, the limit is much, much
larger! (by an order of magnitude!)

I'd only use teraspace if you absolutely can't live with the 16mb limit,
though, as it's not as fast as "regular" memory access.

How well will it perform in comparison to user spaces?  That's really hard
to say. For the first few records, it'll be faster, but the user space
will be moved into memory if you use it enough. In either case, the
amount of RAM on your machine will have a big impact.

One thing though -- if you're already using pointer logic for the user
space, changing it to a memory allocation should be a VERY small change to
your program. It'd almost certainly be worth the time to at least try it
and benchmark it.

Regarding the 3-index approach that has been posted here by others... that
ALSO sounds like a good strategy that will probably help a lot. In that
case, you're using a better algorithm instead of just using a technique
that's "closer to the metal." I'd definitely look at that idea first.

HTH