Search

Top 60 Oracle Blogs

Recent comments

May 2013

Java 7 EE Launch : June 12th & 13th

The Oracle ACE program recently invited members to a teleconference session about the upcoming launch of Java 7 EE. Arun Gupta took us through a preview of the information that will be available to everyone as part of the launch.

If you are interested in getting the low down on this new release, you can register for the launch events here.

Cheers

Tim…

Oracle Security Class and software for Oracle security

I have just agreed a public class dates of my very popular " How to perform a security audit of an Oracle database " with Oracle University to be held on September 24th and 25th in Rome, Italy. The registration....[Read More]

Posted by Pete On 30/05/13 At 05:54 PM

BGOUG Spring 2013 : Photos

I was a little bit rubbish and forgot to get photos of the recent BGOUG event. Fortunately, the conference photos have arrived. You can check them out here.

There are a number of photos of an old fat guy that looks a little like me. I don’t remember meeting him though. Weird… I think he needs the toilet in this shot.

Forcing Smart Scans on Exadata – is the _serial_direct_read parameter safe to use in production?

One of the most common Exadata performance problems I see is that the direct path reads (and thus also Smart Scans) don’t sometimes kick in when running full scans in serial sessions. This is because in Oracle 11g onwards, the serial full segment scan IO path decision is done dynamically, at runtime, for every SQL execution – and for every segment (partition) separately. Whether you get a direct path read & smart scan, depends on the current buffer cache size, how big segment you’re about to scan and how much of that segment is actually cached at the moment. Note that the automatic IO path decision for index fast full scans is slightly different from table scans.

Forcing Smart Scans on Exadata – is the _serial_direct_read parameter safe to use in production?

One of the most common Exadata performance problems I see is that the direct path reads (and thus also Smart Scans) don’t sometimes kick in when running full scans in serial sessions. This is because in Oracle 11g onwards, the serial full segment scan IO path decision is done dynamically, at runtime, for every SQL execution – and for every segment (partition) separately. Whether you get a direct path read & smart scan, depends on the current buffer cache size, how big segment you’re about to scan and how much of that segment is actually cached at the moment. Note that the automatic IO path decision for index fast full scans is slightly different from table scans.

Forcing Smart Scans on Exadata – is the _serial_direct_read parameter safe to use in production?

One of the most common Exadata performance problems I see is that the direct path reads (and thus also Smart Scans) don’t sometimes kick in when running full scans in serial sessions. This is because in Oracle 11g onwards, the serial full segment scan IO path decision is done dynamically, at runtime, for every SQL execution – and for every segment (partition) separately. Whether you get a direct path read & smart scan, depends on the current buffer cache size, how big segment you’re about to scan and how much of that segment is actually cached at the moment. Note that the automatic IO path decision for index fast full scans is slightly different from table scans.

Forcing Smart Scans on Exadata – is the _serial_direct_read parameter safe to use in production?

One of the most common Exadata performance problems I see is that the direct path reads (and thus also Smart Scans) don’t sometimes kick in when running full scans in serial sessions. This is because in Oracle 11g onwards, the serial full segment scan IO path decision is done dynamically, at runtime, for every SQL execution – and for every segment (partition) separately. Whether you get a direct path read & smart scan, depends on the current buffer cache size, how big segment you’re about to scan and how much of that segment is actually cached at the moment.

Forcing Smart Scans on Exadata – is the _serial_direct_read parameter safe to use in production?

One of the most common Exadata performance problems I see is that the direct path reads (and thus also Smart Scans) don’t sometimes kick in when running full scans in serial sessions. This is because in Oracle 11g onwards, the serial full segment scan IO path decision is done dynamically, at runtime, for every SQL execution – and for every segment (partition) separately. Whether you get a direct path read & smart scan, depends on the current buffer cache size, how big segment you’re about to scan and how much of that segment is actually cached at the moment. Note that the automatic IO path decision for index fast full scans is slightly different from table scans.

French Philosophy

From Mohamed Houri, here’s a French translation of all my “Philosophy” notes to date.

How to hint

Here’s a live example demonstrating a point I’ve often made – you have to be very detailed in your hinting or Oracle will find a way to obey your hints and do the wrong thing.  A recent posting on the OTN database forum gave use the following query and execution plan: