Re: 11gR2 smart flash cache

From: Jeremy Schneider <>
Date: Wed, 12 Jan 2011 16:35:57 -0600
Message-ID: <>

One quick note on this... direct reads do not always indicate temp (or even parallel). In 11g Oracle will sometimes start using direct path reads for serial full tablescans.

I recently observed this happening a lot with one of my clients. FYI, I believe that this particular database had an underconfigured SGA... might be related. Interestingly, because Oracle was doing so many FTS with direct path, the BCHR looked deceptively healthy.


Steve Harville wrote:
> I have not tried this setting but I do have some experience with
> Oracle on flash drives.
> We are an EMC shop so most I/O is already cached (all writes and all
> sequential reads). The system cannot cache random reads so that is
> where I use flash drives. The temp tablespace can benefit the most
> from flash drives since it exhibits this read pattern. If "direct
> reads" are a large part of your total wait time then you can probably
> benefit from moving temp to flash.
> Steve Harville
> On Wed, Jan 12, 2011 at 5:24 AM, Zhu,Chao <> wrote:
>> hi, List friends,
>> Oracle has been promoting this flash cache as second tier cache for
>> oracle for a while; Just wondering whether anyone has used this within the
>> industry?
>> We typically have 30gb-60gb SGA supporting 1TB-4TB database; We found
>> usually 30gb or 60gb cache size does not really matter much for majority of
>> our database(some has big diff though, depends on workload profile/active
>> dataset); But a 300gb flashdisk might make huge difference, and help reduce
>> the IOPS load on the SAN side?
>> Looking forward to industry experience;
>> Thx
>> --
>> Regards
>> Zhu Chao

+1 312-725-9249

Jeremy Schneider

Received on Wed Jan 12 2011 - 16:35:57 CST

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