SUMMARY: priority_paging and Veritas Quick I/O

From: Caparrosso, Nelson T. (
Date: Mon Aug 14 2000 - 14:12:04 CDT

A handful of replies point to enabling priority_paging in all systems
regardless of underlying FS and memory models. Priority Paging
(, is
supposed to fix the traditional paging mechanism problem wherein during
heavy filesystem I/O, application pages are stolen by filesystem paging
resulting in a significantly slowed down system.

The reason for this post is that there virtually is no official stand from
Veritas and SUN on enabling priority_paging on systems that employ Quick
I/O. Veritas Quick I/O allow files sitting on filesystems to behave as 'raw
devices' thereby avoiding the system buffer. And since priority_paging is
supposed to only benefit systems that do a lot of I/O on filesystems, we've
gotten quite a bit confused whether there's any real benefit in enabling it.

We've employed it and it seems to have virtually lessened paging on our
systems and our wait I/O's have dramatically fallen to acceptable levels.

Many thanks to those that have responded. I am attaching their replies as a
separate file.

Original POST:
> Esteemed Gurus:
> We are running Oracle 8.1.6 on UE servers, Solaris 2.6 in which we employ
> Veritas Database Edition with its Quick I/O feature. Quick I/O allows us
> to treat database files (on Filesystems) as character device files thereby
> giving us some semblance of raw I/O bypassing the system buffers. May
> question is : is it still necessary to enable priority_paging on Quick I/O
> DB environments - the fact that we're nearer raw in most of our I/O?
> Thanks and I will summarize.
> ------------------------------------------------------------------
> UNIX/Microsoft/GIS Consultant
> Decision Consultants, Inc
> Internet :
> Disclaimer: All views & opinions in this e-mail are mine alone!
> ------------------------------------------------------------------
> <<replies.txt>>

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