Re: DB writers

Chao-Ping Chien (pchien_at_noc.tor.hookup.net) wrote:
: I just read an article regarding oracle dbwriter on solaris have a parameter
: in init.ora (async_writes), I am using pyramid NILE, oracle 7.0.15.4, Is this
: parameter also exist on pyramid port ?

: thanks for any info.

Oracle will use Asynchronous I/O for the db_writer process if you have bought and installed the optional Asynchronous I/O Pyramid software option. Check with your Sales contact at Pyramid.

You can check this by doing something like "strings /unix | grep specaio". You should see a line that says "specaio Y 1 0 0 0 0 0 0 0". Alternatively, look in /etc/conf/sdevice.d, and cat specaoi. If the "Y" is a "N", it means you haven't configured async I/O, it may also mean you haven't purchased it!

In your initSID.ora file, make sure db_writers = 1. You can check that the db_writer is using async writes by doing "truss <pid>" on the dbwr process. Periodically, you should see "ioctl" calls, rather than the normal "write".

Performance for heavily write intensive environments (Eg. OLTP) will benefit from Asunc I/O. When the database checkpoints, 1 async I/O db_writer is more efficient than multiple synchronous db_writers. Also you save memory by only using 1 db_writer.

If you rarely checkpoint and memory is no issue, benefits will be limited, but atleast you don't have to worry about the optimum number of db_writers for your particular database application,

Jon

--

      -m------- Jon Scott	               Tel : +44 252 373035
    ---mmm----- Pre Sales Support 
  -----mmmmm--- Pyramid Technology Ltd.        jscott_at_pyra.co.uk
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