Re: filesystemio_options setting

From: Finn Jorgensen <>
Date: Fri, 16 May 2008 11:17:14 -0400
Message-ID: <>


> By bypassing the file system cache you need to access the storage system
> more often.
> The storage system needs to keep in it's cache the blocks previously held
> in the file system cache, effectively decreasing the hit ration for the
> cache.
> This increase the number of physical I/Os and thats leads to degradation.

The assumption we've all been making here is that by going to direct IO you move the part of memory that had been used as a filesystem cache to the SGA/db cache. The idea is Oracle is better at managing the cache of it's data than some filesystem which has no idea what's accessing it's data. That negates your logic because the same amount of memory is being used as cache, except now Oracle manages all of it.


Received on Fri May 16 2008 - 10:17:14 CDT

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