Re: sga_max_size - pre-allocated at instance startup?

Mladen Gogala wrote:
> On Fri, 03 Mar 2006 15:26:40 -0800, Joel Garry wrote:
>
> > Solaris and hp-ux have always implemented shared memory different from
> > each other in my experience (back to SunOS 1.2 and hp-ux 9). Just
> > because Posix has a service definition and ipc* have the same syntax
> > doesn't mean things work the same, although they are getting closer in
> > more recent Oracle.
>
> Solaris has a perversion called "intimate shared memory, which
> allows processes to share page table as well as the page contents.
> From Oracle 7.3 all the way to 8i there was a parameter called
> "use_intimately_shared_memory", which was supposed to be set to true
> on Solaris. That parameter would enable Oracle to use XXX-shared
> memory and gain some performance. Another thing with which many

On 7.3, it could gain a _lot_ of performance. I got burned the first time I did a big imp not knowing about this (having used a number of other unix but been off Solaris for a few years). use_ism was the parameter. And it didn't work on some hardware/software combinations.

> vendors were toying was the post-wait pseudo device, which was
> faster then the semaphore operations. It was originally developed
> by SGI but I've seen it on AIX and Solaris as well.
> I do believe that Oracle was using classic shmget,shmat and similar
> calls wherever available and would switch to specialized libraries,
> based on parameters. Of course, I never worked for Oracle and I've
> never seen the source code, so I don't really know.
>

jg

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