RE: Async_io set up HP-UX for 10g Instances(these are apps instances)

Fyi this sums up the topic nicely:


From: Adrian [mailto:adex.turner@xxxxxxxxx] 
Sent: 06 August 2007 19:36
To: 'edwin_kodamala@xxxxxxxxx'; 'rxsherm@xxxxxxxxxxxxx';
'knecht.stefan@xxxxxxxxx'; 'ax.mount@xxxxxxxxx'; 'exriscer@xxxxxxxxx'
Cc: 'oracle-l@xxxxxxxxxxxxx'
Subject: RE: Async_io set up HP-UX for 10g Instances(these are apps




You can only simulate asynchronous I/O as per the note. This is not the same
as having kernel level asynchronous I/O, as there will be overheads.


Even so, the available throughput may be sufficient for your requirement. I
suggest you try it and see.





From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
On Behalf Of edwin devadanam
Sent: 06 August 2007 16:01
To: rxsherm@xxxxxxxxxxxxx; knecht.stefan@xxxxxxxxx; ax.mount@xxxxxxxxx;
Cc: oracle-l@xxxxxxxxxxxxx
Subject: Re: Async_io set up HP-UX for 10g Instances(these are apps


Hi All,


Please add ur valuable comments on the below mentioned points.


This is production database:


SQL> show sga

Total System Global Area 3215950016 bytes
Fixed Size                   741568 bytes
Variable Size            1056964608 bytes
Database Buffers         2147483648 bytes
Redo Buffers               10760192 bytes

1) As discussed we can't use disk_asynch_io=true in HP-UX(its using jfs not
raw filesystem)
2) Is HP-UX(JFS) doesnt suport asynchronous io?(operating system level)
3) dbwr_io_slaves=x or db_writer_processes=y which one does asynchronous
i/o?(refer Note:47328.1)
4)Keeping db_writer_processes=y only will i not achieve asynchornous i/o?

Thanks In Advance,


Roby Sherman <rxsherm@xxxxxxxxxxxxx> wrote:

> - disk_asynch_io is used to enable the oracle kernel to make use of 
> asynchronous io, IF the OS supports it.

And you really DO want to figure out if your OS supports it. 
Otherwise if you turn it on and its not supported, your database is 
essentially making two I/O calls for every one... One to aio_write 
(which fails) and then an immediate call to pwrite after. I can't 
tell you how many environments I come into where disk_asynch_io is 
set to true and it isn't supported.





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