IO Problem or wrong configuration?

Question

Hi,
i've a server Linux 64bit with 16Gb Ram in which is installed Oracle 11.2.0.2
My datafile are situated under a Volum Group named VgGrop01.
Top show me constant 20-30% wait io, iostat show me 98-100% utilization of vg.
Every query that perform a db file sequential read brings disk usage at 100%.
Which test i can perform to show me if there are disk or db problems?

Answer 1

Hemant K Chitale wrote:
>filesystemio_options=SETALL
This bypasses the filesystem cache.  I find the filesystem cache useful on Linux.
If you are using SETALL, ensure that your db_cache_size is increased so that caching still happens in the SGA.
>Avg Rd(ms) of datafiles ar about 4-7ms  (from AWR)
That's about normal likely using a SAN cache
>In Segments by Logical Reads
Logical Reads are reads from the database buffer cache *not* 'db file sequential read' calls and physical I/O.
You need to isolate the SQL operations that do generate physical reads 'db file sequential / scattered reads'
Hemant K Chitale
Thank you.
I'm using AMM.
buffer cache Advisor show me:
                                   Est
                                  Phys      Estimated                   Est
    Size for  Size      Buffers   Read     Phys Reads     Est Phys % dbtime
P    Est (M) Factr  (thousands)  Factr    (thousands)    Read Time  for Rds
D      2,224   1.0          274    1.0      5,062,295    5,578,817     31.6
D      2,288   1.0          282    1.0      5,031,895    5,451,026     30.9
D      2,496   1.1          307    1.0      4,955,437    5,129,626     29.1
D      2,704   1.2          333    1.0      4,896,189    4,880,572     27.7
D      2,912   1.3          359    1.0      4,847,382    4,675,406     26.5
I've not high beneficts increase buffer cache.
Now i'm looking for
Segments by Physical Reads
                                           Subobject    Obj.      Physical   Pct
Owner      Tablespace Object Name          Name         Type         Reads Total
MYUSER     TBS_DAT    TAB_ANAG_RES                      TABLE   12,406,897  68.2
There are many statements that uses like '%xxxxx%' on a description field.
This cause a full scan.
Can this optimized using Oracle text?