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

Cheng,    

  metalink note: 47328.1 says:
  If you set DISK_ASYNCH_IO to false, then you should also set DBWR_IO_SLAVES to a value other than its default of zero in order to simulate asynchronous I/O.            

  Regards,
  Edwin.K

LS Cheng <exriscer_at_gmail.com> wrote:
  Dude we all have told you you cannot use AIO with Filesystems!

If you really really want to use AIO with Filesystems then buy Veritas Quick I/O. That does support AIO with Filesystem but using Cluster Filesystems.

Thanks

--
LSC


  On 8/6/07, edwin devadanam <edwin_kodamala_at_yahoo.com> wrote:     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,
  Edwin.K
    
Roby Sherman <rxsherm_at_interealm.com> 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. 

--Roby
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