Re: SGA size

Is this too much for one box? Probably, though if its for testing only, fair enough.

Check your init.ora paramters. SHARED_POOL_SIZE can come down. DB_BLOCK_BUFFERS can also be reduced. Make sure LOG_BUFFER is not set to something daft (1Mb should be plenty). And those are the three components of the SGA over which you have immediate control. DB_BLOCK_SIZE also plays a part -but changing that requires you to recreate the entire database.

Check also JAVA_POOL_SIZE -the default is 20M, and the minimum in 8.1.7 is 32K. If you're not using Java very much, shrink it right down to the minimum.

Also LARGE_POOL_SIZE: if you're not using Multi-threaded server, IO_SLAVES or RMAN, get rid of that line altogether -you don't need it. If you are using any of those things, then keep it, because you do.

Bear in mind that no init.ora file changes take effect until you've shutdown and restarted ("bounced your instance"). Which I'm sure you already knew, but I'm just trying to be thorough!

Other than that, there's not a lot to sizing the SGA in purely 'how do I do it' terms. Other posters are hinting at the fact that there are "right" sizes for all these parameters, and that determining what those right sizes are is a matter of performance tuning... which is as much an art form as it is a science. But if you just want to get all 8 instances at least started, and never mind performance, then go for it: shrink the parameters I've mentioned down.

Finally, remember the Oracle rule of thumb which says that your Instance should never take up more than 1/3rd to one half of your available RAM (on the grounds that O/S paging will be induced if you do). In your case, make that "the sum of all 8 Instances should not be more than 512Mb to 725ish Mb" -my maths are poor, but you'll know what I mean, I hope!

Best of luck
HJR

--

Oracle Resources : http://www.geocities.com/howardjr2000
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"Jim Poe" <jpoe_at_fulcrumit.com> wrote in message
news:9rnibc$m0v_at_dispatch.concentric.net...


> We have

>   W2K server

>   Oracle 8.1.7

>   30 gig HDD.

>   1.5GB ram

>   P3 Xenon processor

>

> We want to run 8 instances on this box.  They are small databases, some

> testing, some development, and one for version control.  Right now we can

> only get 7 up and running.  The eighth gives us 'ORA_27101 : shared memory

> realm does not exist'. I am assuming this is due to the fact that we don't

> have the SGA sized correctly.

>

> How should I set the SGA size for each instance?  Are there other

parameters


> I should be looking at.  Is this too much for one box?

>

> Thanks

>

>

> --

> Jim Poe (jpoe_at_fulcrumit.com)

>

>