Postgres vs. Oracle access paths – intro

This is the start of a series on PostgreSQL execution plans, access path, join methods, hints and execution statistics. The approach will compare Postgres and Oracle. It is not a comparison to see which one is better, but rather to see what is similar and where the approaches diverge. I have a long experience of reading Oracle execution plans and no experience at all on Postgres. This is my way to learn and share what I learn. You will probably be interested if you are in the same situation: an Oracle DBA wanting to learn about Postgres. But you may also be an experienced Postgres DBA who wants to see a different point of view from a different ‘culture’.

I’ll probably use the Oracle terms more often as I’m more familiar with them: blocks for pages, optimizer for query planner, rows for tuples, tables for relations…

Upgrading an Amazon EC2 Delphix Source, Part III

This is the Part III in a four part series on how to:

  1.  Enable VNC Viewer access on Amazon EC2 hosts.
  2.  Install DB12c and upgrade a Dsource for Delphix from 11g to 12c, (12.1)
  3.  Update the Delphix Configuration to point to the newly upgraded 12c database and the new Oracle 12c home.
  4.  Install DB12c and upgrade target VDBs for Delphix residing on AWS to 12.1 from the newly upgraded source.

In Part II, we finished upgrading the Dsource database, but now we need to get it configured on the Delphix side.

Installation overview of node_exporter, prometheus and grafana

Prometheus is an open source systems monitoring and alerting toolkit originally build at Soundcloud. This blogpost shows how to install the needed components to do visualisation of linux system statistics via Grafana.

The setup consists of 3 components:
node_exporter, an exporter of system and hardware metrics.
prometheus, a metric collection and persistence layer.
grafana, the visualisation layer.

1. Preparation
The needed components are installed in the home directory of the user ‘prometheus’. In order for that user exist, it must obviously first be created:

Upgrading an Amazon EC2 Delphix Source, Part II

I’m finally getting back to upgrading the Linux Source for a POC I’m doing with some folks and picking up from where we left off in Part I

Address Display Issue

Now that we have our VNC Viewer working on our Amazon host, the first thing we’ll try is to run the Oracle installer, (unzipped location –> database –> runInstaller) but it’s going to fail because we’re missing the xdpinfo file.  To verify this, you’ll need to open up a terminal from Application –> System Tools –> Terminal:

Step-By-Step SLOB Installation and Quick Test Guide for Amazon RDS for Oracle.

Before I offer the Step-By-Step guide, I feel compelled to answer the question that some exceedingly small percentage of readers must surely have in mind–why test with SLOB? If you are new to SLOB (obtainable here) and wonder why anyone would test platform suitability for Oracle with SLOB, please consider the following picture and read this blog post.

Linux memory usage

One of the principal important configuration settings for running an Oracle database is making appropriate use of memory. Sizing the memory regions too small leads to increased IO, sizing the memory regions too big leads to inefficient use of memory and an increase in memory latency most notably because of swapping.

On Linux, there is a fair amount of memory information available, however it is not obvious how to use that information, which frequently leads to inefficient use of memory, especially in today’s world of consolidation.

The information about linux server database usage is available in /proc/meminfo, and looks like this:

Redo OP Codes:

This posting was prompted by a tweet from Kamil Stawiarski in response to a question about how he’d discovered the meaning of Redo Op Codes 5.1 and 11.6 – and credited me and Julian Dyke with “the hardest part”.

Over the years I’ve accumulated (from Julian Dyke, or odd MoS notes, etc.) and let dribble out the occasional interpretation of a few op codes – typically in response to a question on the OTN database forum or the Oracle-L listserver, and sometimes as a throwaway comment in a blog post, but I’ve never published the full set of codes that I’ve acquired (or guessed) to date.

Fast Now, Fast Later

The following is the text of an article I published in the UKOUG magazine several years ago (2010), but I came across it recently while writing up some notes for a presentation and thought it would be worth repeating here.

Fast Now, Fast Later

The title of this piece came from a presentation by Cary Millsap and captures an important point about trouble-shooting as a very memorable aphorism. Your solution to a problem may look good for you right now but is it a solution that will still be appropriate when the database has grown in volume and has more users.

I was actually prompted to write this article by a question on the OTN database forum that demonstrated the need for the basic combination of problem solving and forward planning. Someone had a problem with a fairly sudden change in performance of his system from November to December, and he had some samples from trace files and Statspack of a particular query that demonstrated the problem.

The $50 Million Hyphen

There are a plethora of mishaps in the early space program to prove the need for DevOps, but Fifty-five years ago this month, there was one in particular that is often used as an example for all.  This simple human error almost ended the whole American space program and it serves as a strong example of why DevOps is essential as agile speeds up the development cycle.  

Upgrading an Amazon EC2 Delphix Source, Part I

For a POC that I’m working on with the DBVisit guys, I needed a quick, 12c environment to work on and have at our disposal as required.  I knew I could build out an 11g one in about 10 minutes with our trust free trial, but would then need to upgrade it to 12c.

Disable snapshots to Delphix Engine

This is a simple prerequisite before you upgrade an Oracle source database and takes down the pressure on the system, as well as confusion as the database upgrades the Oracle home, etc.

Simply log into the Delphix Admin console, click on your source group that the source database belongs to and under Configuration, in the right hand side, you’ll see a slider that needs to be moved to the “disable” position to no longer take interval snapshots.