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Oracle datawarahouse: i/o stuff

Occasional Visitor

Oracle datawarahouse: i/o stuff

Hi, We're quite new with HP-UX & Oracle.
We have a new warehouse system running on an NPAR(4 cpu and 4 gb ram). HP-UX 11i and Oracle
Trying to understand two things actually.
First the combination of OS parameters afftecting async i/o.
Plus are there any guidelines for mount options of oracle filesystems. (DB is no arc mode.)

Eric Antunes
Honored Contributor

Re: Oracle datawarahouse: i/o stuff

Hi Omer,

We are precisly discussing this on this thread:


Each and every day is a good day to learn.
Jean-Luc Oudart
Honored Contributor

Re: Oracle datawarahouse: i/o stuff


welcome to the forum !

There are a good few threads on the subjects.
I had a similar question regarding mount options for oracle DB

also check this thread :

What is the backend storage ?

fiat lux
Occasional Visitor

Re: Oracle datawarahouse: i/o stuff

We're using HDS 9980V as backend storage.

Oracle :
dbwr_io_slaves :8
db_writer_processes :1
disk_asynch_io TRUE

max_async_ports 50
aio_listio_max 256
aio_max_ops 2048
aio_physmem_pct 10
aio_prio_delta_max 20
fs_async 0
dbc_max_pct 10
dbc_min_pct 5

We have realized that oracle filesystems are all mounted with log option default mincache and convosync options.
Before looking into db, we wanted to take a look at OS site and found some configuration issues like these.

Honored Contributor

Re: Oracle datawarahouse: i/o stuff


concerning async i/o, the following kernel parameters needs to be reviewed:

a. max_async_ports limits the maximum number of processes that can concurrently use /dev/async

b. aio_max_ops limits the maximum number of asynchronous i/o operations that can be queued at any time. Set this parameter to the default value (2048)

also read metalink note: 139272.1 "HP-UX: Asynchronous i/o"

No person was ever honoured for what he received. Honour has been the reward for what he gave (clavin coolidge)
Occasional Visitor

Re: Oracle datawarahouse: i/o stuff

We've checked that our kernel is not compiled with async driver. Since our oracle datafiles reside on filesystems not raw devices we're not using async i/o behaviour. right? So what is impact of having dbwr_io_slaves :8 and
db_writer_processes :1 set.I think that, in this situation using mutliple dw writers instead of io slaves may provide some performace gain.

Occasional Visitor

Re: Oracle datawarahouse: i/o stuff

Many thanks for the extra info.