Search

Top 60 Oracle Blogs

Recent comments

June 2016

Installing EM13c on Windows Tips

I just built out my own EM13c environment so I can answer many questions that I won’t be able to ignore just because I no longer work at Oracle.

Yes, You Must Use CALIBRATE_IO. No, You Mustn’t Use It To Test Storage Performance.

I occasionally get questions from customers and colleagues about performance expectations for the Oracle Database procedure called calibrate_io on XtremIO storage. This procedure must be executed in order to update the data dictionary. I assert, however, that it shouldn’t be used to measure platform suitability for Oracle Database physical I/O. The main reason I say this is because calibrate_io is a black box, as it were.

The procedure is, indeed, documented so it can’t possibly be a “black box”, right? Well, consider the fact that the following eight words are the technical detail provided in the Oracle documentation regarding what calibrate_io does:

This procedure calibrates the I/O capabilities of storage.

Do, There Is No Try

I know Werner DeGruyter will like the title of this post, so here’s a post dedicated to him as my last week at Oracle is off to a busy start…. </p />
</p></div></div>

    	  	<div class=

Little things worth knowing: auto-DOP or hint-which one takes precedence?

This is just another short post about one of the little things worth knowing. Assume you are on 12.1.0.2 for example and you want to know if parallel_degree_limit reliably keeps the degree of parallelism at bay, for all sessions and queries across the board. After all, every machine has finite CPU (and other) resources that shouldn’t be exhausted. Setting parallel_degree_limit of course only has an effect if you set parallel_degree_policy to limited, auto or adaptive. The latter is the Big Knob to enable Automatic Degree Of Parallelism (DOP), and the post assumes that Auto DOP is enabled for the session. In this configuration, what happens to hinted statements?

Documentation

The documentation (12c Reference Guide, section on parallel_degree_limit) states that you can provide an integer in addition to “CPU” and “IO”:

Major and Minor keys in Oracle NoSQL Database

Oracle NoSQL Database uses Major and Minor key values to achieve user-controllable record co-location. Records are stored based on the hash of the major key, so all of the records with the same major key will be co-located on the same server.

Oracle Cloud v/s Amazon Cloud

A few years ago, I taught an online class in Oracle Database administration for the University of Washington. Every student was given their own virtual machine in the Amazon cloud for the duration of the class, courtesy of Amazon. It was ridiculously simple to clone, start, stop, and destroy virtual machines using the Amazon CLI (command line interface). All students had full SSH and SQL*Net access to their virtual machines in the Amazon cloud. At that time, Oracle had a pitiful cloud offering: a single schema on Oracle Database 11g, a maximum of 50 GB of database storage, and no Oracle Net (SQL*Net) access

Storing Date Values As Numbers (The Numbers)

In my last couple of posts, I’ve been discussing how storing date data in a character based column is a really really bad idea. In a follow-up question, I was asked if storing dates in NUMBER format was a better option. The answer is that it’s probably an improvement from storing dates as strings but it’s […]