Solaris Asynchronous I/O & Oracle

Hi,

I am wondering if anyone can shed any light on the matter of Asynchronous I/O (or AIO) on Solaris 2.3 with Oracle 7.0.16.4.

I have my datafiles partitioned on five different disks, which is not to be confused with raw devics (as this is not an option for me, unfortunately), and wonder if I can set the parameter async_write=true to perform asynchronous writes!!!. This enables asynchronous writes (would you believe), on a Solaris system, but the documentation says that this is only possible on raw devices, yet I have used this on the database with five disks, which are not raw devices, and the database still retrieves data when queried, does ORACLE bypass this parameter if not applicable. Is there something that I have missed ??!!

Something else I tried was the fact that I set db_writers (in the init.ora file) to 10, but when looking at a book by Corrigan & Gurry called ORACLE PERFORMANCE TUNING there is listed various parameters for optimisation related to db_writers. One of the parameters is DB_BLOCK_WRITE_BATCH, but when I list parameters in SQLDBA it does not appear. It appears as an underscored parameter, which I suppose ORACLE have decided to make obsolete because of some enhancement. Would setting db_writers to 10 make any difference when a couple of the derived parameters cannot be altered?? And is having a large number of multiple database writers of any use in terms of performance (despite what the documentation says) ??

In total I am looking for better I/O throughput. As far as I understand setting the async_write=true is a better option than having multiple database writers (i.e. setting db_wrtites=10).

Has anybody any thoughts or revelations on this matter ?

Cheers

Inte

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Inte Ali

inte_at_uk.ac.warwick.dcs

Department of Computer Science
University of Warwick
England


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Inte Ali