WOW I'm busy! Thats a good thing but it sure slows down my blog posting. I apologize for that. I've been working on my latest rant essay to post here, but it's not done yet, and I really should do something Oracle 11g related, so here it is!
As you may know, 11g now manages both the SGA and the PGA automatically though some new parameters, memory_size and memory_max_size.
Memory_size replaces sga_size and pga_aggregate_target, combining the two into one memory pool for Oracle to manage (well, not really one big memory pool, they are still separate, but Oracle deals with all the details under the covers).
Memory_max_size is roughly like sga_max_size + pga_aggregate_target, gobbling up memory for future use should you use it.
So, why the comment about /dev/shm? If you are going to move to 11g's flavor of memory management on Linux, then you might run into this little error:
ORA-00845: MEMORY_TARGET not supported on this system
and you might say to yourself, "Wow, that stinks, I can't use memory_target on Linux."
Well, thats not quite the case. In fact, the problem is likely that /dev/shm is not configured big enough. You will get this error if /dev/shm is not configured large enough to handle the memory you are allocating with memory_target. So, if you are planning on using these new features, be preparing now and increase the size if /dev/shm.
More on this and many other topics in my new Oracle Database 11g New Features book which is available for pre-sales now on Amazon.com. It will be out VERY SOON!!!