DB2_PARALLEL

DB2_PARALLEL_IO

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

mitrofun63@gmail.com - 25 Oct 2007 10:05 GMT

Hello

In our environment we have one RAID10 volume builded on 16 disks (IBM
EXP810 enclosoure) and 3 logical drives on this volume for our
databases.
All tablespaces in databases are created with 4 containers per
tablespace. (currently its not possible to change)
Also, for all tablespaces PAGESIZE=16384, EXTENTSIZE = 2,
PREFETCHSIZE=8 and the segment size on RAID10 volume is 128K.

Do i need to enable DB2 profile variable DB2_PARALLEL_IO=* or in my
case this is not optimal for disks read/write perfomance ??

DB2 9.1.2 on AIX5.3 TL4

Thanks
With best regards, Dmitry

Reply to this Message

Kiran Nair - 28 Oct 2007 19:11 GMT

Hi Dmitry,
So you have a system which has as single LUN in SAN made out of 16
disk in 8+8.
And you have 3 LVM's made of this hdisk.
And you have 4 containers per Table space ?
That should mean you have more than one containers in single mount.

Did you start loading the database ? Did you monitor how much is the
disk busy (in topas) ?

If not it would be better to monitor the os and also the SAN (are you
using DS4000 Series ? ).

>From my experience, I have seen, single container per tablepspace in

san is far faster than multiple containers.
DB2_PARALLEL_IO helps in getting the number of parallelism and also
when your PREFETCHSIZE is automatic.

Probably you need change this only if your DB2 is showing far a lot of
IO problems. And if so, best way would be enable this for a day and
see how the system performs.
But if you put your prefetchsize as automatic, you may need to change
the value as DB2_PARALLEL_IO=*:8 .

Depending on your bufferpool, you can play around with the IO variable
to put more data in BP if your data access is more sequential. Its
difficult to change the EXTENDSIZE, I would have have 16 as intial
value and PREFETCH size as automatic as initial configuration of the
system.

Regards
Kiran Nair

On Oct 25, 5:05 pm, mitrofu...@gmail.com wrote:

> Hello
>
> In our environment we have one RAID10 volume builded on 16 disks (IBM

> EXP810 enclosoure) and 3 logical drives on this volume for our
> databases.
[quoted text clipped - 10 lines]
> Thanks
> With best regards, Dmitry

Reply to this Message

dunleav1 - 31 Oct 2007 20:08 GMT

Has anybody seen any issues with this not working correctly on Linux
with DB2 9 FP3 ?
How can I verify that parallel streams are being utilizied?
I use DB2_PARALLEL_IO=*:3 and I have set no file system caching on my
tablespaces as well...

Reply to this Message