Checking VXFS QIO usage

This isn’t something new however given that i saw this problem at a customer just last week, i would like to point to something you have to keep in mind when using Oracle DB with the Veritas Filesystem. When you have strange performance problem when using VXFS please ensure that the database isn’t sitting around in the POSIX inode r/w-lock with it’s database writes. Check if Quick-I/O (solves the issue) or ODM (solves the issue as well) is really activated. QIO is not activated by just using the FILESYSTEMIO_OPTION=setall or by mounting the filesystem with the mount option qio. You have to do more and it looks like this is sometimes forgotten by people setting up or migrating a system. So far this test was the fastest for me because it checks if something is present that shouldn’t present when QIO is in action:

echo '::threadlist -v' | mdb –k | sed 's:^$:§:' | tr -d '\n' | tr '§' '\n' | grep 'vx_rwsleep_rec_lock'  | tr  -s ' ' | cut -d ' ' -f 10 | sort | uniq -c

When this command line returns with oracle processes containing “dbw” you should really check if you have properly configured QIO or ODM. Please refer to the VXFS documentation in regard of the correct installation and configuration steps. You will find the explanation for this at this rather old blog entry: “Hunting red herrings”