direct path read & db_file_multiblock_read_count
- From: "Hameed, Amir" <Amir.Hameed@xxxxxxxxx>
- To: 'ORACLE-L' <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 25 Oct 2013 22:21:38 +0000
Hi Folks,
Here is the environment configuration:
- RHEL 6/u4
- Cisco UCS 16xcores & 128GB RAM
- Oracle RDBMS 11.2.0.3 (Oracle ERP database)
- db_cache_size=6G
- pga_aggregate_target=2G
- db_file_multiblock_read_count8 (this is not set exclusively and is
being set by the Oracle kernel based on the value of db_cache_size)
I am running the following query to force a FTS:
select /*+ full(GLL) */ count(*) from GL_JE_LINES GLL
union all
select /*+ full(FA) */ count(*) from FA_BALANCES_REPORTS_ITF FA
;
When I trace the session with 10046/level 8, I see that most of the 'direct
path read' are being done with cnt as shown below:
grep 'direct path read' n22vt2_ora_9850_Linux.trc|awk '{print $13}'|sort|uniq
-c|sort -k 1 -n
...
288 cnt
307 cntH
1345 cnt8
3493 cnt
48942 cnt
This is quite consistent on all environments on Linux. On Solaris, a similar
type of statement shows that most of the DPR are done with cnt8.
Does anyone know what might be causing Oracle to choose 16 blocks as opposed to
the larger 128 blocks reads.
Thanks,
Amir
--
//www.freelists.org/webpage/oracle-l
Other related posts:
