From: Paul Harrison <>
Date: Thu, 15 Mar 2012 15:27:23 -0500
Message-ID: <001401cd02ea$079bdb70$16d39250$>

Does the RDBMS instance request the extents per query or does it store then for later use(other queries) ?

-----Original Message-----
From: [] On Behalf Of Martin Berger
Sent: Thursday, March 15, 2012 3:18 PM
Subject: Re: RAC

the best source I have found:

Oracle Automatic Storage Management: Under-the-Hood & Practical Deployment Guide

File Open
When an RDBMS instance needs to open an ASM file, it sends to the ASM instance a file-open request, with the filename, via one of the o0nn processes. ASM consults the File Directory to get the extent map for the file. ASM sends the extent map to the RDBMS instance. In Oracle Database 10g, for datafiles, ASM sends the entire extent map to the RDBMS instance at file-open time. In Oracle Database 11g, for datafiles, ASM initially sends the 60 direct extents to the RDBMS instance. For the remaining extents, which are located in indirect extents, the RDBMS requests subsequent extent map sections on demand.
ASM delivers all the extent map pointers in the same indirect extent as the requested file extent.

does this answer your question?

On Thu, Mar 15, 2012 at 19:03, Paul Harrison <> wrote:
> Hi All,
> RAC.. In database instance... I query for some data and the database
> instance has to communicate with the asm instance in order to get the
> path to the block within the asm disk group. Does the asm instance
> return all the pointers to the blocks one time(one round trip) or round
trip per block?
> Thanks,
> Paul
> --


Received on Thu Mar 15 2012 - 15:27:23 CDT

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