Voice of the DBA

Tag: syndicated

  • Unlimited Vacation

    Unlimited Vacation sounds good, and maybe it works, but I wonder how much vacation people really take at Red Frog. My guess is that it’s not far off from what most progressive companies give, something like 20 days a year.

    It’s a good perk to have, and I’m sure it doesn’t get abused since the people that abuse it get let go. The people that don’t abuse it might even shortchange themselves. I know it sounds like a company would have people taking 40, 50, maybe 100 days a year off, but the reality is that if someone does that you find yourself in one of two situations:

    • their work isn’t getting done and you fire them
    • their work is getting done and you ignore it.

    There are plenty of managers that might feel they should be getting more work from someone that can take 100 days a year off and still get their work done, but what type of attitude is that? You hire someone, expect them to get xx things done in a year for yyy dollars. If they get xx things done in 2/3 year while the person next to them takes a year, why complain? If others complain, tell them to just get their work done quicker (or learn how to work more efficiently).

    I get over 20 days, plus holidays, and I struggle to take it. I’m essentially in the same boat as the Red Frog employees in that I manage my own schedule, and can take off whenever I want if my work is done. I rarely take sick days, since I can work at home when I’m sick. I have a grinding, daily job that requires regular effort, so I can’t plan on a month project, take off 2 days in the middle and catch up later. I essentially run a newspaper, every day.

    However I could take unlimited vacation. I could potentially get my work done in 3 days every week, keeping enough items scheduled, to take two days a week off. I’m just not sure that it would be vacation since I’d be stressed during those 3 days.

    If you are a professional, I think most places will work with you to get the vacation you need, whether it’s tracked, booked, managed, or not. The key, in my opinion, is to set a schedule that works for you, and a set amount of work that justifies your salary and makes both you and your employer happy.

  • T-SQL Tuesday #26 – Second Changes with Date/Time

    TSQL2sDay150x150

    I missed the very first T-SQL Tuesday, so when this month’s topic of second chances came up, I decided to write that one.

    If you are unsure of what T-SQL Tuesday is, follow the link to this month’s topic to get the rules and description and then write a blog post.

    Date/Time Challenges

    I picked an easy one, but one that I continue to see asked in the forums by people new to SQL Server. I suspect we’ll see less questions over time as more people take advantage of the new DATE and TIME datatypes in SQL Server 2008 and later, but maybe not. Lots of people are still sure that they need to keep those items together.

    In any case, have you ever seen sales data like this:

    OrderID     OrderDate               CustomerID  OrderAmount
    ———– ———————– ———– ————
    1           1982-05-19 06:31:48.950 1           579040.5070
    2           1994-11-27 17:14:41.790 2           348808.5860
    3           1972-11-08 17:40:01.170 3           758992.3650
    4           1972-05-31 01:19:05.530 4           779853.1990
    5           1994-12-22 10:40:57.410 5           666173.8040
    6           1974-04-03 01:42:29.490 6           134218.2330
    7           1976-06-22 15:21:18.910 7           322938.6950
    8           1953-08-05 23:00:34.620 8           14169.7580
    9           1971-08-16 22:33:28.970 9           586057.3820
    10          2002-03-28 13:08:00.420 10          632785.0760

    Here’s some DDL, you can create your own data, but here are a few rows:

    CREATE TABLE SalesOrders
( OrderID INT IDENTITY(1,1) , OrderDate DATETIME , CustomerID INT , OrderAmount NUMERIC(10, 4) ) INSERT SalesOrders (OrderDate, CustomerID, OrderAmount) VALUES ( '1982-05-19 06:31:48.950', 1, 579040.5070), ( '1994-11-27 17:14:41.790', 2, 348808.5860), ( '1972-11-08 17:40:01.170', 3, 758992.3650), ( '1972-05-31 01:19:05.530', 4, 779853.1990), ( '1994-12-22 10:40:57.410', 5, 666173.8040)

    If I want to get all the sales in May of 1972, I get query them all like this:

    SELECT OrderDate
, OrderAmount
 FROM SalesOrders
 WHERE OrderDate > '1972/5/1' AND OrderDate <= '1972/5/31'

    I get 4 rows back. That’s something people often write when they get input from a user. A user has a start and end edit box, they enter “1972/5/1’” in the start box (or use a calendar picker) and then enter “1972/5/31” in the other. I’m using ISO dates to make this clear, though in the US it would normally display like “5/1/1972” and in the UK as “1/5/1972”.

    However, that isn’t quite correct. If I run this query:

    SELECT OrderDate
, OrderAmount
 FROM SalesOrders
 WHERE MONTH(OrderDate) = 5
  AND YEAR(OrderDate) = 1972

    I actually get 6 rows. The data rows for May 1972 are:

    OrderDate               OrderAmount

    ———————– —————————-

    1972-05-31 01:19:05.530 779853.1990

    1972-05-13 09:26:52.590 676848.9700

    1972-05-28 21:05:28.840 923425.0510

    1972-05-07 10:59:09.930 266079.6480

    1972-05-01 04:21:01.250 464241.6480

    1972-05-31 01:19:05.530 779853.1990

    What’s happening?

    If you look at the OrderDates for May 31, you see two values that have a time of 1:19:05am. Those are excluded from the query, which has an end date of “1972/5/31”. Why? This query:

    SELECT CAST( '1972/5/31' AS DATETIME)

    shows why. It returns:

    1972-05-31 00:00:00.000

    That’s midnight between the 30th and 31st, which is before 1:19:05am. When a datetime value is converted in SQL Server, without a time component, it defaults to the beginning of the day. That works great for the start date, not so good for the end date.

    Fixing this

    There are two real fixes here. Well, maybe more. You can query on the month and year, but those functions can disrupt indexes, so I don’t recommend them. The two main fixes are:

    • add a time component
    • add a day

    The first fix is the addition of the last time of the day to your query.

    SELECT OrderDate
, OrderAmount
 FROM SalesOrders
 WHERE OrderDate > '1972/5/1' AND OrderDate <= '1972/5/31 23:59:59.997PM'

    In some type of code, it looks more like this:

    DECLARE @end DATETIME SELECT @end = '1972/5/31' SELECT @end = @end + '23:59:59.997' SELECT OrderDate
, OrderAmount
 FROM SalesOrders
 WHERE OrderDate > '1972/5/1' AND OrderDate <= @end

    Assume the first select is actually coming from the user.

    The second fix is to add a day, and actually query like this, which is what I’d recommend:

     SELECT OrderDate
, OrderAmount
 FROM SalesOrders
 WHERE OrderDate > '1972/5/1' AND OrderDate < '1972/6/1'

    In this case, instead of querying for May 31, we move to June 1 (the next day) and then change the <= to a < only. This gets all orders occurring up until the end of May 31, but before June 1.

    Easy fixes, but so often there’s code that doesn’t allow for the time component. Take a minute and check your reports, and be sure you aren’t underreporting any data to your clients or customers.

    Also be sure to check out the new datatypes in SQL Server 2008 and later:

  • DBAs in Denver

    I have a friend looking for a production DBA in Denver, so if you’re interested, email me at SQLServerCentral.

    They need a production DBA in the South Denver area, backups, config, query tuning, replication, partitioning. SQL Server 2005-2008 R2.

  • Capacity planning for new hardware

    I get asked this question a lot: When getting a new application and database, what kind of hardware do I need?

    The answer is easy: it depends.

    It depends on

    • the load you will put on the SQL Server instance.
    • on the SLA and performance numbers you need.
    • the uptime you need to maintain (RPO/RTO factor in here)

    There are other factors, but essentially the server needs enough hardware to handle the workload in the time you need it to handle things.

    It doesn’t depend on

    • the number of users
    • the number of databases
    • the size of the databases*

    A slight asterisk on the last one. The size of the databases matter for the space you need to buy, but they don’t necessarily affect the RAM or CPU you need. The number of users and databases can contribute to load, but those numbers of a vacuum don’t affect the hardware. I have a test machine with dozens of databases, and it generates no load. Why not? No workload, or not much of one.

    The same thing applies to users. If the users do a lot of work, making changes, querying large data sets, it can be a loaded database. However I had a database one time that had 5,000 clients. It was updated by agent software on desktops in our company every hour. However each update was a singleton update to a specific row, and it was comfortably hosted on a 2CPU, 2GBRAM Standard SQL Server 2000 instance.

    How do I plan?

    Photo Jan 03, 8 50 26 AM

    This is a tough question in many ways. I have searched all over, and asked questions, and even written a SQL University week on it (overview, disk, other). There are two main scenarios here, but they both get similar treatment.

    You have to test your workload against hardware and see what happens. It can be a simulated one, or if you have an existing instance being upgraded, take a real workload.

    There are numerous replay tools or testing tools, but the bottom line is you have to simulate the way you use SQL Server on actual hardware. You can do some extrapolation, but don’t expect it to be a linear change.

    For example, if I have a dual core CPU of xx type, with 1GB of RAM and a 2 drive R1 array, I can’t assume I’ll get twice as much performance with a quad core of the same type with 2GB of RAM and 2 R1 drives. It almost becomes an art to examine the memory usage, the IOPS you are generating, and the percentage of CPU. As you scale up, the usage of those three values might changes and shift. More RAM can reduce IOPS and CPU, especially in reads, but not necessarily. If you have a 1TB table you’re constantly summarizing, you might not get much better performance going from 1 -> 2GB.

    Ultimately it’s a bit of a guess for most of us. Fortunately most of our workloads can be handled by hardware since most databases are relatively small. Test, make some guesses, and go a little big, especially on RAM and CPU. Those are the hardest to add later, from my experience. It seems people expect disks to fill up and we need more space, but it’s often harder to approve CPU/memory upgrades, especially if it requires newer motherboards.

    I wish I had a better answer, and there are numerous articles that don’t seem to me to do a better job, but read as much as you can, and try to learn how others view their systems. Then make your own guesses about what is best for your system.