DBA Tips Archive for Oracle


[an error occurred while processing this directive]

No Title

[an error occurred while processing this directive]

by Michael New, MichaelNew@earthlink.net, Gradation LLC

To activate time measurements in Oracle, the DBA will need to turn on timed_statistics parameter either during database startup via the init.ora file or using an ALTER SYSTEM common.

Starting with Oracle9i, Oracle now supports capturing certain performance data with microsecond (µs) granularity. Views that include microsecond timing include the following.

Performance Views with Microsecond (µs) Granularity
View Name Column Name

Existing columns in other views continue to use centisecond times.

Because microsecond timing might not be appropriate for rolled-up data, STATSPACK displays most times in seconds. It displays average times in milliseconds for easier comparison with operating system monitoring utilities, which often report timing in milliseconds.

For clarity, the time units used are specified in the column headings of each timed column in the Statspack report. The following conventions are used.

If timings are available, the STATSPACK report orders wait events by time. These are listed in the Top-5 and background and foreground wait events sections.

If TIMED_STATISTICS is FALSE for the instance, but a subset of users or programs set TIMED_STATISTICS to TRUE dynamically, then the STATSPACK report output can look inconsistent, where some events have timings (those which the individual programs/users waited for) and some do not. The Top-5 section also looks unusual in this situation.

Optimally, TIMED_STATISTICS should be set to TRUE at the instance level, for ease of diagnosing performance problems.

Copyright (c) 1998-2017 Jeffrey M. Hunter. All rights reserved.

All articles, scripts and material located at the Internet address of http://www.idevelopment.info is the copyright of Jeffrey M. Hunter and is protected under copyright laws of the United States. This document may not be hosted on any other site without my express, prior, written permission. Application to host any of the material elsewhere can be made by contacting me at jhunter@idevelopment.info.

I have made every effort and taken great care in making sure that the material included on my web site is technically accurate, but I disclaim any and all responsibility for any loss, damage or destruction of data or any other property which may arise from relying on it. I will in no case be liable for any monetary damages arising from such loss, damage or destruction.

Last modified on
Tuesday, 17-Jan-2012 10:14:11 EST
Page Count: 8458