RE: Tablespace and Table storage options

From: Kevin Closson <kevinc_at_polyserve.com>
Date: Wed, 11 Oct 2006 08:37:51 -0700
Message-ID: <5D2570CAFC98974F9B6A759D1C74BAD001C331BB@ex2.ms.polyserve.com>

 >>>it's even worse than that.  You said you were on an 8k block

>>>size, and the largest read I see from the reads below is 8
>>>blocks (see the P3 value). So, you're only reading 64k at a
>>>time. So, something is limiting your multiblock reads to
>>>64k. Likely, this is an O/S or filesystem limitation.

I too am interested in this OS information as well as what db_file_multiblock_read_count is set to. I know of no OS where library support for scattered read is arbitrarily limited to something as small as 64KB and that includes port implementations to readv, lio_listio, preadv and odm_io.

It is conceivable that the device driver is limited to 64KB and that the port engineer at Oracle build knowledge in the OSDs for that disk type to throttle multiblock reads regardless of init.ora settings... I've been there and done that with VME->scsi disks way back in the mid 90s which had, get this, 60KB max transfer size. So the Sequent ports had to be smart enough to know that of the underlying device was VME->scsi, we had to throttle the scan I/O sizes or I/O would fail.

--
http://www.freelists.org/webpage/oracle-l

Received on Wed Oct 11 2006 - 10:37:51 CDT