Voice of the DBA

Author: way0utwest

  • Risk Analysis

    I saw a post recently that talked about disaster recovery being an important part of your company’s systems and that you needed to be sure that you could recover everything in the event of a disaster. That’s a common perception we all have, but I noticed that another person had replied that we shouldn’t necessarily make DR a huge priority. Our DR spending ought to be inline with the risk of a disaster, and the actual costs, or losses, resulting from downtime.

    The decision on what to spend for DR can be answered by the classic DBA response, “it depends,” but I thought this Friday I might ask anyway.

    What do you spend on DR?

    I am asking as a percentage of your budget, or even the cost of running your large systems. Do you know what is spent? Do you know how to find out?

    I’m curious how involved many of you are in the DR process? Do you consider it a part of the application development? Do you think about the failure when the system is being put together and ensure that the setup or rebuild is easier in the future?

    This is an area that I think many companies ignore and count on things going their way. That’s not a great strategy, but it works for many companies. Most of us never have major disasters, and can usually fumble through small ones.

    I think that over time there will be less tolerance for the bumbling, keystone cops efforts of most IT shops. Our systems are  more integrated into businesses and there’s less possibility of even rolling back to non-computerizes systems in many cases.

    Thinking about DR earlier, and making the investment to ensure some level of DR is in place is the sign of a more mature business. And a more mature IT professional.

    Steve Jones

  • SQL Saturday Advice – Speaker Communication

    Recently I was at an event and a speaker wasn’t able to make a session. There was a minor scramble, and the session ended up being cancelled, which is fine, but it got me thinking about what I would do if I had an emergency.

    I don’t always have the contact information for organizers, and it’s not easily available. In some cases, I’m not sure how I’d get in touch with someone. I usually have an email, but not always, and I think my emergency solution would be to “tweet” that I wouldn’t be there with the hashtag for the event and hope someone picks it up.

    However I think there’s a better solution. In the speaker communication the last week before the event, let all speakers know that they are expected to meet their commitments and give them 2 or 3 phone numbers to call for issues. Make sure those people keep their cell phones handy and can respond.

    I’d also be sure you have address, phone, and map links for all the locations for speakers. I know most should be local, but spending a few minutes including links in the emails will help ensure that speakers have a smooth event and are happy to come back again.

  • Common SQL Server Mistakes – Equals NULL

    One thing that I don’t see a lot, but it still happens with people new to SQL Server is the comparisons they’ll make with NULL values. Often those people new to T-SQL will write this:

    select CustomerID, CustomerName
    from Customers
    where SalesRepID = NULL

    The thought here is they are looking for those customers that don’t have a salesrep assigned. Or they might enclose the NULL in quotes, but this won’t work.

    The correct way to do this is:

    select CustomerID, CustomerName
    from Customers
    where SalesRepID Is NULL

    Note the “Is NULL” that will correctly return those customers who have a NULL value stored in that column.

    Why?

    NULL is an unknown value. We just don’t know what value it is, so it’s not a variable in algebra like “x”. In algebra, x=x, but NULL != NULL. Since we don’t know what the value is, and since each row could potentially have a different value (remember every NULL’s value is unknown) we can’t expect any NULL to equal any other NULL.

    NULL isn’t a placeholder like a blank or space, or even zero. It’s an unknown value, so equals (and not equals) does not apply. Instead you need to use “Is NULL” or “Is Not NULL” for your comparisons.

  • Yikes!

    I don’t love traveling, but after reading this, I am not sure I want to fly anymore. Perhaps I should take fewer trips next year, or stick to those events that I can drive to?

    The link is about a plane that supposedly had malware introduced into the airline computer network from a USB drive. The plane subsequently crashed and although it’s debatable whether or not the software was the cause, it’s an issue that needs to be examined.

    We use more and more computer systems in our lives, especially in our transportation. Planes, trains, and automobiles, all are becoming more and more computerizes, which I like, but the linkages between all their computer systems is something that concerns me.

    It seems that every few months we are constantly finding new ways in which computer systems can be hacked, altered, or changed, despite tremendous efforts on the part of software vendors. I’m not sure that we’ll ever completely secure our systems, which means that the more interconnections, and more access points we have, the more likely that someone will be able to introduce some type of malware into the system.

    Which could have extremely serious consequences for our safety.

    I don’t like the idea of a USB port in my car having any linkage to the mechanical controls, and I certainly don’t think that this should exist in airplanes. We ought to have a good separation of systems so that a failure or security breech in one, can’t affect any others.

    Steve Jones