Re: High mbrc in aux

From: fairlie rego <fairlie_r_at_yahoo.com>
Date: Fri, 10 Mar 2006 16:41:55 -0800 (PST)
Message-ID: <20060311004155.25452.qmail@web31914.mail.mud.yahoo.com>

Hi,

I have seen this generally to be incorrect in 9.2 and I set it manually using dbms_stats.set_system_stat.

The default value is -1 but that happens when you do not have enough multiblock reads during your sampling period.

Regards,
Fairlie

"Allen, Brandon" <Brandon.Allen_at_OneNeck.com> wrote: Anybody seen this before?

Oracle 9.2.0.5 on AIX 5.2:

SQL> show parameter db_file_multiblock_read_count

NAME TYPE VALUE
------------------------------------ ----------- -----
db_file_multiblock_read_count integer 16

execute dbms_stats.gather_system_stats('START');

. . . run batch jobs for 8 minutes . . .

execute dbms_stats.gather_system_stats('STOP');

SQL> select * from sys.aux_stats$;

SNAME PNAME PVAL1 PVAL2
------------------------------ ------------------------------ ---------- ----------------

SYSSTATS_INFO STATUS COMPLETED
SYSSTATS_INFO DSTART 03-10-2006 14:22
SYSSTATS_INFO DSTOP 03-10-2006 14:30
SYSSTATS_INFO FLAGS 1
SYSSTATS_MAIN SREADTIM 3.864
SYSSTATS_MAIN MREADTIM 10.811
SYSSTATS_MAIN CPUSPEED 546
SYSSTATS_MAIN MBRC 97 <----???
SYSSTATS_MAIN MAXTHR 2957312
SYSSTATS_MAIN SLAVETHR -1

Notice the MBRC figure of 97 even though I have db_file_multiblock_read_count=16. I searched Metalink for bugs and known issues but no luck. I guess the next step is to peform a 10046 trace and check the p3 value for all the 'db file scattered reads', but I figured I'd check to see if any of you have already seen this before I go to that trouble.

Thanks,
Brandon

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http://www.freelists.org/webpage/oracle-l Received on Fri Mar 10 2006 - 18:41:55 CST

Re: High mbrc in aux_stats$