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March 2014

Diagnostics

Here’s a little test you might want to try. Examine the following script, and decide what sort of symptoms you would see in the AWR report.


create global temporary table gtt1(n1 number);

execute dbms_workload_repository.create_snapshot;

insert into gtt1 values(1);
truncate table gtt1;

-- repeat insert/truncate for a total of 100 cycles

execute dbms_workload_repository.create_snapshot;

-- generate an AWR report across the interval.

I don’t need anyone to tell me their results – but if your predictions and the actual results match then you can give yourself a pat on the head.
You might also like to enable SQL trace for all the inserts/truncate to see if that shows you anything interesting.

This is one of the simpler scripts of the 3,500 I have on my laptop that help me interpret the symptoms I see in client systems.

[Oracle] DB Optimizer Part XI - Query transformation fixes false cardinality estimation with multiple OR predicates (in newer Oracle releases)

Introduction

This is a short blog post about another query transformation (check my first blog post [Oracle] DB Optimizer Part VIII - Looking under the hood of query transformation (done by CBO) with simple real life example first, if you never heard of the term "query transformations"), that fixes a cardinality estimation issue with multiple (OR) predicates that cover the whole data range. I have to admit that this is a special case, but it can happen as observed by my client

Min/Max

One of my most-repeated observations about trouble-shooting Oracle is that things break when you start combining features. Here’s an example that demonstrates the point.

It’s possible to create “descending” indexes – or indexes with descending columns, as I prefer to call them, and there’s a special “min/max range scan” optimizer operation for a particular kind of index usage – demonstrated in the following code fragment (running under 11.2.0.4, and reporting the rowsource execution statistics):

Min/Max

One of my most-repeated observations about trouble-shooting Oracle is that things break when you start combining features. Here’s an example that demonstrates the point.

It’s possible to create “descending” indexes – or indexes with descending columns, as I prefer to call them, and there’s a special “min/max range scan” optimizer operation for a particular kind of index usage – demonstrated in the following code fragment (running under 11.2.0.4, and reporting the rowsource execution statistics):

Java 8 Released

Java 8 released! Download it here... Oracle continues to beat Sun’s track record for actually updating Java on a regular basis. Java 8 brings many exciting new features and many miscellaneous improvements including:
• Java tippy-toes into the world of “Functional” programming with the addition of Lambda expressions; not quite a “Closure” but Lambdas allow the definition of stand-alone methods tied to the java.util.Function interface; functional methods are perfect for one-time code needs
• Annotations may be used anywhere a Type is used; not just at Type declaration
• New java.util.Stream API allows functional style operations on streams of elements in collections providing the ability to perform bulk operations such as map-reduce
• HashMap improvements
• Compact profiles to allow Java to function in low-resource environments

COLLABORATE 14 - IOUG Forum

Event date: 
Mon, 2014-04-07 - Fri, 2014-04-11

We are pleased to announce that the annual Oracle users conference COLLABORATE 14 - IOUG Forum will take place in Las Vegas from April 7-11, 2014 at the Venetian and Sands Expo Center.  This is a once-a-year opportunity to connect with the members of not one but three Oracle users groups (IOUG, OAUG and Quest) as well as with the top names and faces in the Oracle community.

First Week at Oracle

I was warned it would be difficult.  I was warned that it would be time-consuming and painful, but I survived without as much as a scratch on me.

This last week was my first week at Oracle and it was really, really great.  The on board process wasn’t difficult at all.

Maybe it was because I was told to be prepared for a difficult and challenging week, so I was prepared for something very difficult and it was much easier than I imagined.

Chicago Oracle User Community Restart

Chicago is the third largest city in the United States. There are probably more professional Oracle users here than most other areas in the country – and yet for many years now there hasn’t been a cohesive user group.

But right now there’s an opportunity for change. If the professional community of Chicago Oracle users steps up to the plate.

Chicago Oracle User Community Restart

Chicago is the third largest city in the United States. There are probably more professional Oracle users here than most other areas in the country – and yet for many years now there hasn’t been a cohesive user group.

But right now there’s an opportunity for change. If the professional community of Chicago Oracle users steps up to the plate.