Re: MBRC & db_file_multiblock_read_count
Date: Thu, 17 Jan 2008 03:51:54 -0800 (PST)
On Jan 17, 5:53 am, "Yannick ROGER" <yannick.ro..._at_achatpro.com> wrote:
> I'm working on Oracle 10g.
> What is the diffrence between:
> - MBRC setted by dbms_stats.set_system_stats or automaticly with
> - db_file_multiblock_read_count setted in int file?
> Is the scope of these 2 parameters the same?
> Is one override the other?
> Do i have to set the same value for both of them?
> Can you recommend a good doc about this?
Paraphrased from "Cost-Based Oracle Fundamentals": Oracle uses MBRC from the SYS.AUX_STATS$ for cost calculations, but the runtime engine tries to use DB_FILE_MULTIBLOCK_READ_COUNT when performing physical reads. On Start up, Oracle determines the operating system's largest physical read size and silently uses that to limit whatever value is set for DB_FILE_MULTIBLOCK_READ_COUNT.
I believe that Jonathan Lewis now recommends not setting (or at least
experimenting with not setting) the DB_FILE_MULTIBLOCK_READ_COUNT
IT Manager/Oracle DBA
K&M Machine-Fabricating, Inc. Received on Thu Jan 17 2008 - 05:51:54 CST