If you’ve spent much time working in a UNIX environment you’ve probably seen the load averages more than a few times.

load averages: 2.43, 2.96, 3.41

I have to admit that even in my sysadmin days I didn’t fully understand what these numbers were, but Zach did some digging a while ago to try to understand where these numbers are comming from.

In his blog entry from late last year, Zach sums it up quite nicely:

In short it is the average sum of the number of processes waiting in the run-queue plus the number currently executing over 1, 5, and 15 minute time periods.

The formula is a bit more complicated than that, but this serves well as a functional definition. Zach provides a bit more detail in his article and also points out Dr. Neil Gunther’s article on the topic which has as much depth on the topic as anyone could ever ask.

So what does this mean about your system?

Well, for a quick example let’s consider the output below. The load average of a system can typically be found by running top or uptime and users typically don’t need any special privileges for these commands.

load averages: 2.43, 2.96, 3.41

Here we see the one minute load average is 2.43, five minute is 2.96, and fifteen minute load average is 3.41.

Here are some conclusions we can draw from this.

  • On average, over the past one minute there have been 2.43 processes running or waiting for a resource
  • Overall the load is on a down-trend since the average number of processes running or waiting in the past minute (2.43) is lower than the average running or waiting over the past 5 minutes (2.96) and 15 minutes (3.41)
  • This system is busy, but we cannot conclude how busy solely from load averages.

It is important here to mention that the load average does not take into account the number of processes. Another critical detail is that processes could be waiting for any number of things including CPU, disk, or network.

So what we do know is that a system that has a load average significantly higher than the number of CPUs is probably pretty busy, or bogged down by some bottleneck. Conversely a system which has a load average significantly lower than the number of CPUs is probably doing just fine.

Easy Linux CommandsFor more tips like this check out my book Easy Linux Commands, only $19.95 from Rampant TechPress.

UNIX, systems administration, sysadmin, solaris, linux, load averages, system monitoring, sun, mac, osx

Oracle 9iR2 Data WarehousingAbout a year an a half ago I was right in the middle of researching data warehouse technologies and starting to get quite discouraged on the lack of good technical books on the topic. Then I came across the book “Oracle9iR2 Data Warehousing” by Hobbs, Hillson and Lawande. Here’s the review I put on Amazon on this deep technical book.

In this book, the authors take you swiftly and thoroughly through the entire process of creating a data warehouse. Several other books (I purchased 4 others before this) over-generalize the topic, teaching the vocabulary and business reasons for data warehousing. This book teaches how to implement a warehouse in Oracle 9i Revision 2, while teaching the major concepts through practical application.

It would be easy to get bogged down in the technical details of this book if one were not familiar with the Oracle environment. Those who are familiar with Oracle will find it is much like the courses offered by Oracle. The book consistently, clearly presents the concepts (dimensions, fact tables, summaries, ETL) then delves into such depth it leaves the reader with a complete understanding of not only how to implement each concept, but when, and why to implement them.

The major concepts covered include dimensional modeling, data partitioning, query optimization, materialized views, dimensions, the extract-transform-load process, warehousing tools, ongoing warehouse maintenance, and many more. Furthermore, SQL for the examples used in the book are available from one of the authors websites, affording the reader a hands-on environment in which to observe these concepts.

Overall, I would recommend this book to anyone looking to work with warehousing who already has a firm Oracle background (strong knowledge of schemas, data dictionary, storage conventions, terminology.) This is simply the best book I have found on data warehousing.

I see that there is now a new version of this book out. “Oracle Database 10g Data Warehousing” by the same authors, plus Pete Smith, will go on my short list for tech books to buy.

oracle, data warehouse, database, dba, database administration, data warehousing

In a previous article Oracle conditions and how they handle NULL I give some examples on how NULL is evaluated in Oracle. After talking with Scott, a student who is doing some database work with me this semester I believe I may have a better way of explaining the initially cryptic evaluation of NULL.

NULL in Oracle is essentially considered a non-answer. For example let’s consider this yes/no question:

Are you currently living in the USA?

There are two obvious answers to this question, Yes and No, but we need to be prepared for one more circumstance, a non-answer.

So if you ask me this question and I don’t answer it can you say “Jon is currently living in the USA”? No. Can you say “Jon is not currently living in the USA”? No! We can’t compare against something we don’t know so any comparisons against NULL are treated as false.

To handle these circumstances in Oracle we must use IS NULL and IS NOT NULL to detect these non-answer values. For some examples of this code and more detail on this check out my original article on the topic.

database, database administration, database programming, dba, oracle

It looks like Oracle is re-aligning themselves with Sun Solaris as their preferred 64-bit platform. In the March issue of Oracle Magazine they have a short announcement on the topic:

Oracle has chosen the Solaris 10, Sun Microsystems’ multiplatform, open source operating system, as its preferred development and deployment platform for most 64-bit architectures. Solaris 10 will be used throughout Oracle’s development organization, and Oracle will release and ship 64-bit versions of all Oracle products on Solaris prior to, or simultaneously with, release on other operating systems.

Check out the whole article here or sign up to get your free copy of Oracle Magazine.

Thanks to Jon G. for sending this on to me.

oracle, database, database administration, dba, systems administration, sysadmin, solaris, sun, sun microsystems, UNIX, open source, 64-bit

EditPlus in actionWhile there are many text editors out there offering a broad set of features my favorite right now is EditPlus.

EditPlus is a Windows shareware application designed for text, HTML, Java, PHP, etc. It’s very thin requiring little (nearly no) load time and has many great features such as:

  • Syntax hilighting for many languages
  • EditPlus on Windows right-click
  • FTP and SFTP integration
  • Templates
  • Line Numbering
  • Column Selection
  • Optional Spell Checker

The list of features is long and every revision brings more. Check out the Features page for more.

I’ve been using the Oracle 9iR2 syntax file from the user files section of EditPlus.com and it seems to pick up all the SQL and PL/SQL syntax I use, although many other syntax files exist and you could always make your own.

As mentioned above, EditPlus is shareware. A single user license is only $30, and with discounts for buying in bulk there is no reason not to pay, but for now, download it, try it, and see why you can’t live without it.

Thanks to Zach for showing this to me a couple years ago.

text, text editing, editing, editor, edit, sql, plsql, pl/sql, sftp, ftp, notepad, wordpad, oracle, unix, php, perl, programming, database programming, dba, database administration, systems administration, c, c++, java, javascript, css, html

« Previous PageNext Page »