Directio

How To Verify Whether DIRECTIO is Being Used [ID 555601.1]

• Use directiostat from http://www.solarisinternals.com/si/tools/directiostat/index.php

or

$ ps -ef |grep _dbw
$ truss -aefo /tmp/truss.out -p 2260

Look for the ioctl call made after the open of a datafile, typically this will look something like:

	19483: ioctl(3, 0x2000664C, 0x00000001) = 0 

The 3rd argument value of 1 is used for DIRECTIO_ON, and 0 would be seen if a call was made with DIRECTIO_OFF.

• This sample is for new sqlplus session.

truss -f -t open,ioctl -u ':directio' sqlplus "/ as sysdba"

References:

• http://karlarao.tiddlyspot.com/ > DirectIO
• https://blogs.oracle.com/apatoki/entry/ensuring_that_directio_is_active
• http://www.pythian.com/news/22727/how-to-confirm-direct-io-is-getting-used-on-solaris/

• Note that ASM will use AIO & Direct IO automatically.
  • ASM Inherently Performs Asynchronous I/O Regardless of filesystemio_options Parameter [ID 751463.1]
  • Init.ora Parameter "FILESYSTEMIO_OPTIONS" Reference Note [ID 120697.1]

• Pros and Cons of Using Direct I/O for Databases [ID 1005087.1]