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Words I Don’t Use, Part 5: “Wait”

The fifth “word I do not use” is the Oracle technical term wait.

The Oracle Wait Interface

In 1991, Oracle Corporation released some of the most important software instrumentation of all time: the wait statistics that were implemented in Oracle 7.0. Here’s part of the story, in Juan Loaiza’s words, as told in Nørgaard et. al (2004), Oracle Insights: Tales of the Oak Table.

This stuff was developed because we were running a benchmark that we could not get to perform. We had spent several weeks trying to figure out what was happening with no success. The symptoms were clear—the system was mostly idle—we just couldn’t figure out why.

ODA X6 Small Medium Large and High Availability

There are 4 models of Oracle Database Appliance with the new ODA X6 which is for the moment the latest ODA hardware version. One is similar to the previous X5-2 one, and 3 smaller ones known as ODA Lite. They are 1 year old already, here is a small recap of the differences and links to more detail.


The ODA X6 are composed with Oracle Server X6-2:

Join Elimination Bug

A few years ago a bug relating to join elimination showed up in a comment to a post I’d done about the need to keep on testing and learining. The bug was visible in version and, with a script to replay it, I’d found that it had disappeared by

Today I had a reason to rediscover the script, and decided to test it against – and found that the bug was still present.

Here’s the model:

Latest Delphix Blog Post and Upcoming Webinars

In my latest blog post on the Delphix site, I continue my conversation with why DevOps is the next step for DBAs and how DBAs can embrace this next step in their evolution.

Installation of Rundeck with the Ansible plugin on Centos 7

This post shows you how to install Rundeck with the Ansible plugin on Centos 7. The installation is done with nginx as the web server and using SSL with a self signed certificate. Please read the Ansible installation script, and modify anything that should be different for your situation. You will be amazed how well readable the installation script is!

Rundeck is a web based user interface that allows you to run commands against a group of hosts. Rundeck has an ansible plugin. Using that plugin, it could perform the similar functionality as Ansible Tower (commercial product) or Semaphore (open source).

After a fresh installation of Centos 7, do the following as root:

Postgres vs. Oracle access paths VI – Index Scan

In the previous post my queries were still reading the indexed column only, from a table which had no modifications since the last vacuum, and then didn’t need to read table pages: it was Index Only Scan. However, we often need more columns than the ones that are in the index. Here is the Index Scan access path.

Postgres vs. Oracle access paths V – FIRST ROWS and MIN/MAX

We have seen how an index can help to avoid a sorting operation in the previous post. This avoids a blocking operation: the startup cost is minimal and the first rows can be immediately returned. This is often desired when displaying rows to the user screen. Here is more about Postgres startup cost, Oracle first_rows costing, and fetching first rows only.

Here is the execution plan we had in Oracle to get the values of N sorted. The cost for Oracle is the cost to read the index leaves: estimated to 46 random reads:

SQL_ID dbck3rgnqbakg, child number 0

Upgrading an Amazon EC2 Delphix Target, Part IV

It’s finally time to upgrade our Linux Target!  OK, so we’re not going to upgrade the way a DBA would normally upgrade a database server when we’re working with virtualization.

So far, we’ve completed:

  • 1.  Updating our instances so that we’ll have a GUI interface if we’ll need one.
  • 2.  Installed Oracle on the Linux Source and upgraded our Dsource database to 12c


Now we’re done with our Linux Source and onto our Linux Target.

Postgres vs. Oracle access paths IV – Order By and Index

I realize that I’m talking about indexes in Oracle and Postgres, and didn’t mention yet the best website you can find about indexes, with concepts and examples for all RDBMS: You will probably learn a lot about SQL design. Now let’s continue on execution plans with indexes.

Little Things Doth Crabby Make – Part XXII. It’s All About Permissions, Dummy. I Mean yum(8).

Good grief. This is short and sweet, I know, but this installment in the Little Things Doth Crabby Make series is just that–short and sweet. Or, well, maybe short and sour?

Not root? Ok, yum(8), spew out a bunch of silliness at me. Thanks.

Sometimes, little things doth, well, crabby make!