What Is That Light-Green Oracle Database CPU Wait Time?

What Really Is That Light-Green Oracle Database CPU Wait Time?



Have you ever wondered what that light-green "cpu wait time" really means in Oracle Enterprise Manager? It's what I call, the "gap" time. The "gap" time is the "missing" or the "leftover" time when DB Time does not equal the DB CPU (foreground process CPU consumption) plus the non-idle wait time. And, it happens more often than you might think.

If you have ever noticed (more...)

How To Approach Different Oracle Database Performance Problems

How To Approach Different Oracle Database Performance Problems

Jump Start Your Oracle Database Tuning Effort


Every Oracle Database Administrator will tell you no two performance problems are the same. But a seasoned Oracle DBA recognizes there are similarities...patterns. Fast problem pattern recognition allows us to minimize diagnosis time, so we can focus on developing amazing solutions.

I tend to group Oracle performance problems into four patterns. Quickly exploring these four patterns is what this (more...)

I Have Lots Of Oracle Database Server Power But Performance Is Slow/Bad

I Have Lots Of Oracle Database Server Power But Performance Is Slow/Bad


Oracle Database parallelism and serialization is what we as Oracle Database Administrators live and die for. You have a screaming fast Oracle Database system and there is lots of computing power available.

But performance is unacceptable; users are screaming, the phone is ringing, and those fancy dashboards are flashing like it's Christmastime.

What is going on?! What can I do about it?! That's (more...)

Do The LGWRs (10,11,12c) Always Sleep For The Full Three Seconds?

Do The LGWRs (10,11,12c) Always Sleep For The Full Three Seconds?


Back in June I wrote (included a video) about the Oracle Database log writer(s) "3 second sleep rule." That's the rule we were all taught by our instructors when we started learning about Oracle yet never really knew if it was true. In that post, I demonstrated Oracle Database log writer background processes are normally put to sleep for three seconds.

In this (more...)

Can A Background Process Impact A Foreground Process And Its Database Time?

Can A Background Process Impact A Foreground Process And Its Database Time?


Have you ever heard someone say, "Background processes do not impact foreground processes because they run in the background and in parallel with foreground processes." I've heard this hundreds of times!

While doing some DB Time research I came across a great example of how an Oracle Database background process can directly and significantly impact a foreground process.

The above quote represents (more...)

Is Oracle Database Time Correct? Something Is Not Quite Right.

Is Oracle Database Time Correct? Something Is Not Quite Right.


Oracle Database tuning and performance analysis is usually based on time. As I blogged HERE, the Oracle "database time" statistic is more interesting than simply "time spent in the database." It is the sum of CPU consumption and non-idle wait time. And Elapsed Time is the sum of all the database time related to perhaps a session or a SQL statement execution. However...

Changing The Number Of Oracle Database 12c Log Writers

Changing The Number Of Oracle Database 12c Log Writers


In an Oracle Database 12c instance you will likely see multiple log writer (LGWR) background processes. When you first start the Oracle instance you will likely see a parent and two redo workers. This is a very big deal and something many of us have been waiting for - for many years!

While I'm excited about the change, if I can't control the number of LGWRs (more...)

The Perfect Gift For The Oracle DBA: Top 5 DBA T-Shirts

The Perfect Gift For The Oracle DBA: Top 5 DBA T-Shirts


It's that time of year again and I can already hear it, "Dad, what do you want for Christmas?" This year I'm taking action. Like forecasting Oracle performance, I'm taking proactive action.

Like most of you reading this, you have a, let's say, unique sense of humor. I stumbled across the ultimate geek website that has an astonishing variety of t-shirts aimed at (more...)

Off May Not Be Totally Off: Is Oracle In-Memory Database 12c (12.1.0.2.0) Faster?

Off May Not Be Totally Off: Is Oracle In-Memory Database 12c (12.1.0.2.0) Faster?


Most Oracle 12c installations will NOT be using the awesome Oracle Database in-memory features available starting in version 12.1.0.2.0. This experiment is about the performance impact of upgrading to 12c but disabling the in-memory features.

Every experiment I have performed comparing buffer processing rates, clearly shows any version of 12c performs better than 11g. (more...)

Is Oracle Database 12c (12.1.0.2.0) Faster Than Previous Releases?

Is Oracle Database 12c (12.1.0.2.0) Faster Than Previous Releases?


I was wondering if the new Oracle Database 12c version 12.1.0.2.0 in-memory column store feature

will SLOW performance when it is NOT being used. I think this is a fair question because most Oracle Database systems will NOT be using this feature.

While the new in-memory column store feature is significant, with each new Oracle feature there is (more...)

Does Increasing An Oracle Background Process OS Priority Improve Performance?

Does Increasing An Oracle Background Process OS Priority Improve Performance?


Does increasing an Oracle Database background process operating system priority improve performance? As you might expect, the answer is, "It depends."

In this posting I will explain the results of an experiment where I increase the Oracle Database 12c log writer background processes operating system priority.

In my experiment I created a clear CPU bottleneck and the top wait event was log file parallel (more...)

How To Change The Priority Of Oracle Background Processes

How To Change The Priority Of Oracle Background Processes


Before you get in a huf, it can be done! You can change an Oracle Database background process
priority through an instance parameter! I'm not saying it's a good idea, but it can be done.

In this post I explore how to make the change, just how far you can take it and when you may want to consider changing an Oracle background process priority.

11 Tips To Get Your Conference Abstract Accepted

11 Ways To Get Your Conference Abstract Accepted


This is what happens when your abstract is selected!
Ready for some fun!? It's that time of year again and the competition will be intense. The "call for abstracts" for a number of Oracle Database conferences are about to close.

The focus of this posting is how you can get a conference abstract accepted.

As a mentor, Track Manager and active conference speaker I've been helping DBAs (more...)

Comparing SQL Execution Times From Different Systems

Comparing SQL Execution Times From Different Systems


Suppose it's your job to identify SQL that may run slower in the about-to-be-upgrated Oracle Database. It's tricky because no two systems are alike. Just because the SQL run time is faster in the test environment doesn't mean the decision to upgrade is a good one. In fact, it could be disastrous.

For example; If a SQL statement runs 10 seconds in production and runs 20 seconds in (more...)

Top 7 Reasons Why Oracle Conferences Rock!

Top 7 Reasons Why Oracle Conferences Rock!


Why take the time and make the effort to attend an Oracle database conference or Oracle user group meeting? We're all busy, so there had better be some super good reasons to make the effort! For me, the benefits definitely exceed the cost.

There are many different conferences to choose from. There are professional conferences, leadership conferences, scientific conferences and business focused conferences. So why an Oracle Database (more...)

Top 7 Reasons Why Oracle Conferences Are A Waste Of Time

Top 7 Reasons Why Oracle Conferences Are A Waste Of Time


Want to turn a lame Oracle Database conference experience into a great one? You may not believe this, but I think Oracle conferences are a waste of time. That is, unless I take action. I've been to hundreds of Oracle conferences, so I'm kind of an expert in this field.

Here is my "Top 7" list about why Oracle conferences are time suckers and (more...)

Watch Oracle DB Elapsed Time and Wall Time With Parallel Query

Watch Oracle Elapsed Time and Wall Time With Parallel Query


In my recent postings I wrote that when using the Oracle Database parallel query a SQL statement's wall time should be equal to its elapsed time divided by the number of parallel query slaves plus some overhead.

That may seem correct, but is it really true? To check I ran an experiment and posted the results here. The results are both obvious and illuminating.

If (more...)

What Is Oracle Elapsed Time And Wall Time With A Parallelism Twist


What Is Oracle Elapsed Time And Wall Time With Parallelism Twist


In this post I'm focusing on Oracle Database SQL elapsed time, adding parallelism into the mix and then revisiting wall time. What initially seems simple can take some very interesting twists!

If you are into tuning Oracle Database systems, you care about time. And if you care about time, then you need to understand the most important time parameters: what they are, their differences, (more...)

Watch Oracle DB Session Activity With The Real-Time Session Sampler

Watch Oracle DB Session Activity With My Real-Time Session Sampler


Watching session activity is a great way to diagnose and learn about Oracle Database tuning. There are many approaches to this. I wanted something simple, useful, modifiable, no Oracle licensing
issues and that I could give away. The result is what I call the Oracle Real-Time Session Sampler (OSM: rss.sql).

The tool is simple to use.  Based on a number filtering command line (more...)

What Is Oracle DB Time, DB CPU, Wall Time and Non-Idle Wait Time

What Is Oracle DB Time, DB CPU, Wall Time and Non-Idle Wait Time


If you are into tuning Oracle Database systems, you care about time. And if you care about time, then you need to understand the most important time parameters: what they are, their differences, how they relate to each other and how to use them in your performance tuning work.

The key Oracle Database time parameters are elapsed time, database time (DB Time), (more...)