Re: Semaphores Shared memory in Solaris

"Alessandro Deledda" <adeledda_at_it.tiscali.com> wrote in message news:9ph2f2$kck$1_at_pegasus.tiscalinet.it...
> What is the right semaphores/shared memory settings for a Sun Enterprise
> cluster E6500 with 2 nodes, 10 logical hosts with 10 Oracle Enterprise
> Edition 8.1.6 installed and 1 instance for each installation?
>
> RAM 20G
> initparameter processes = 400 for each DB
> SGA for each instance is about 1G;
> Sun Solaris 2.6;
>
> Oracle formula says:
> Instance A = 100 processes
> Instance B = 100 processes
> Instance C = 200 precesses
> SEMMNS=((A=100) + (B=100)) +((C=200)*2) + ((# of instances)*10)=630;
> therefore in my case (400*10)+(400*2)+(10*10)=4900 , is it right?
>
> But these instances are concurrently and i have problems with shared
memory.
> shmmax >= SGA?
> And if this is right what SGA i have to consider, total SGA of 10 instance
> (1G*10) or single SGA of each instance (1G)?
>
> This is the result of my calculation but i'm not sure, Do you think it is
> right?
>
> set shmsys:shminfo_shmmax=4294967295
> set shmsys:shminfo_shmmin=1
> set shmsys:shminfo_shmmni=100
> set shmsys:shminfo_shmseg=10
> set semsys:seminfo_semmni=400
> set semsys:seminfo_semmsl=400
> set semsys:seminfo_semmns=5000
> set semsys:seminfo_semopm=400
> set semsys:seminfo_semvmx=32767
>
> I am very confused and i hope you help me, thanx in advance.
>
>

Are you saying you have installed one and the same version of Oracle *10* times on *one single* server?
For heaven's sake : WHY?
One time would have been more than enough!!!!

I'm not sure why you specify the number of processes for 4 instances and multiply that by then.
Does that mean you have 40!!! instance running on one single server? Those 40 instances would go heavily competing for resources, and the performance will be abysmal.
The correct formula is
(the sum of the number of processes (which means processes in init.ora) *2) plus (10 sempahores * the number of instances. If you have 4 instances running that would mean 440 semaphores. If you have 10 times as much instances running, multiply that by a factor 10.

The amount of virtual memory required is the *sum of the sizes of the individual SGAs*
The Oracle guideline is to limit that sum to one third of *physical* memory.

In short: I don't believe your setup is ever going to work, you need to buy more servers or apply for the Guiness Book of Records.

Hth,

Sybrand Bakker, Senior Oracle DBA Received on Thu Oct 04 2001 - 12:14:31 CDT