Re: 32bit to 64bit

vafanassiev_at_aapt.com.au (Vsevolod Afanassiev) wrote

>

Why do you say that? The basic difference is that instead of dealing with 32bit memory addresses, you know deal with 64bit memory addresses. I doubt that it will be even slightly slower - keeping in mind that this on 64bit hardware & o/s.

> I also suspect that so-called "64-bit" version of Oracle is really 32-bit version
> with 64-bit memory management.

Untrue. Code is code.. is code. Don't confuse that with what the compiler does. I would be very surprise if Oracle uses 32bit calls and thunked that via a kernel layer to 64bit. If that was the case then there would have been a very noticable and consistent performance degradation in Orale 9i 64bit vs. Oracle 9i 32bit.

> With 32-bit Oracle your SGA is limited to approx 2GB (3.75 GB
> if you use ceratin trick described in Metalink article).
> So it only makes sense to use 64-bit Oracle if you want
> SGA bigger than 4 GB.

In my experience it is the hardware vendors driving this. For example, move to HP-UX 11 64bit and you have no choice but 64bit 9i. Of course, you can always install 32bit 8.1.7... but then running 32bit on a 64bit platform is also not the brightest of ideas (unless this is required to get older legacy 32bit executables to run in which case there are other alternatives).

> Not sure what exactly are the circimstances
> that require very large SGA.

A very large SGA is not something to scoff at... I can think of a couple of things I can do with a 6+GB SGA... :-)

--
Billy