Wrong Results

Some very important MOS Notes when you upgrade and patch

Posted on May 27, 2021 by Mike.Dietrich Patch Recommendation 16

Today, I would like to publish only a short blog post with some hints to MyOracle Support (MOS) notes we find quite helpful. The idea of all these notes I will list below is to help you finding the right patches before you upgrade or patch to Oracle 19c. So see our collection of Some very important MOS Notes when you upgrade and patch below.

Some very important MOS Note when you upgrade and patch

Photo by Jacques Dillies on Unsplash

Why do you need patch bundles?

At first, it is always our recommendation to upgrade to the most recent Release Update (RU). This is currently Oracle 19.11.0 while I’m …

_rowsets_enabled – Apply patch and use the default

I while back I blogged about issues with “rowsets“, a new Oracle 12c feature which unfortunately had two known wrong result (WQR) bugs:

Switch off “_rowsets_enabled” in Oracle Database 12c

UPDATE: _rowsets_enabled in Oracle Database 12c

What does “rowsets” actually mean?

I’d like to thank Sankar, our Development manager for providing this explanation which sheds some light on how important this feature actually is:

“Rowsets is a SQL execution performance enhancement introduced in Oracle RDBMS release 12.1 and further extended in a future release of the Oracle Database.

Prior to 12.1, data processing in the SQL layer were

What happened to the blog post about “12c parameters”?

Posted on February 25, 2016 by Mike.Dietrich Optimizer Parameters Performance Tuning 3

Two weeks ago I published a blog post about Parameter Recommendations for Oracle Database 12.1.0.2. And I took it down a day later. Why that?

I’ve got a lot of input from external sources for the “Parameter” blog post. And I’d like to thank everybody who contributed to it, especially Oracle ACE Ludovico Caldara.

Generally there was a bit of a misunderstanding internally about whether we should “advertise” underscore parameters to cure some misbehavior of the database. In 99% of all cases I’d agree that underscores are not a good solution – especially when it comes …

UPDATE: _rowsets_enabled in Oracle Database 12c

Posted on November 16, 2015 by Mike.Dietrich Flaws and Pitfalls Optimizer Oracle Database 12c Parameters 9

Please find a recent update here:

_rowsets_enabled – Apply patch and use the default

Last week I did post this entry with a strong recommendation to disable _rowsets_enabled in Oracle Database 12.1.0.2:

Nov 10, 2015:
Switch off _rowsets_enabled in Oracle Database 12c

Today I can give you an update, more insight information and better workarounds.

Credits go to our DWH and Optimizer people (thanks to Hermann, Angela, Nigel and Mohammed).

When is the problem happening?

When a hash join operation receives rowsets from its right input but then produces one row at a time as output. This explains …

Switch off “_rowsets_enabled” in Oracle Database 12c

Posted on November 10, 2015 by Mike.Dietrich Flaws and Pitfalls Optimizer Oracle Database 12c Parameters 1

Please find a recent update here:

UPDATE: _rowsets_enabled in Oracle Database 12c

and more important:

_rowsets_enabled – Apply patch and use the default

Twitter is a good thing. I get alerted on things I haven’t seen before. And sometimes some things are more than interesting.

This one is actually proven by Jonathan Lewis – and you can read all the details in Jonathan’s blog post here:

https://jonathanlewis.wordpress.com/2015/11/09/wrong-results/

There seems to be a realistic chance to get wrong query results displayed (regardless of using SQL*Plus or a JDBC or any other client – see the comment by Stefan Koehler below …

Things to consider BEFORE upgrading to Oracle 12.1.0.2 to AVOID poor performance and wrong results

Posted on July 30, 2015 by Mike.Dietrich Flaws and Pitfalls Optimizer 8

Finally it got published on MyOracle Support (MOS) portal – one of the most helpful notes when we prep for an upgrade or a migration – and potentially the one with the longest title in MOS:

MOS Note: 2034610.1
Things to consider BEFORE upgrading to Oracle Database 12.1.0.2 to AVOID poor performance and wrong results

Avoid Poor Performance and Wrong Results when upgrading to 12.1.0.2

One important note regarding these “Things to Consider” notes:
They will only list issues where either a fix or a proven workaround is available. They don’t list all open issues nor do they recommend every given underscore which may cure one or the other misbehavior.…

Avoid Poor Performance and Wrong Results in 11.2.0.4

Posted on April 17, 2014 by Mike.Dietrich MyOracle Support Optimizer Oracle Database 11g Patch Recommendation 18

One of the best notes in MOS got refreshed last night for Oracle Database 11.2.0.4. It has not only information about performance bugs but also about the worst and meanest category of issues, wrong query result bugs. Those are the ones I call the “sleeping beauties” as you as a DBA usually won’t recognize them. It is recognized at the application level when the result of a report is incorrect or instead of 4 rows just 3 rows get delivered in the output. Therefore you should be highly aware of those and add this note to your …

Wrong Results

Some very important MOS Notes when you upgrade and patch

Why do you need patch bundles?

_rowsets_enabled – Apply patch and use the default

What does “rowsets” actually mean?

What happened to the blog post about “12c parameters”?

UPDATE: _rowsets_enabled in Oracle Database 12c

When is the problem happening?

Switch off “_rowsets_enabled” in Oracle Database 12c

Things to consider BEFORE upgrading to Oracle 12.1.0.2 to AVOID poor performance and wrong results

Avoid Poor Performance and Wrong Results in 11.2.0.4

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