When applying a new SQL Server cumulative update, hot fix, or upgrade SQL Server doesn’t always apply all the fixes in the patch. When you upgrade the database engine in-place, databases you had already stay at their pre-upgrade compatibility level, which means they run under the older set of optimizer rules. Additionally, many optimizer fixes are not turned on. The reason for this is that while they may improve overall query performance, they may have negative impact to some queries. Microsoft actively avoids making breaking changes to its software. To avoid any negative performance impacts, Microsoft has hidden optimizer fixes behind a trace flag, giving admins the option to enable…
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Awhile back, if you are on Twitter, you can probably recall my ranting about the 949 indexes I was reviewing. The process was to determine duplicate indexes and consolidate them or discard the unneeded ones. My ranting was not about the duplicates per se it was about the index names. It only takes a second to name an object with some name that tells what the thing is. Below I will show you some examples and give you an easy script that will help you generate your index names. Taking a little time to name things appropriately can go a long way, it can not only be time saving but…
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Okay, here is a pet peeve of mine, I think every stored procedure, function, view etc. should all contain a block of code I refer to as a preamble. If yours doesn’t I strongly recommend you start adding it. It drives me crazy when I see code with no documentation of any kind telling me what it is for and when it was written or changed. Why? A preamble documents the use, need, and changes for the code. It also leaves bread crumbs as to how why and what you did. I don’t know about you but I may code something and not have to change it for two years.…
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Today I ran into something on a client server I unfortunately see too often. The DBA goes through the trouble of configuring and setting up alerts\operators but doesn’t really understand what the options in the configurations mean. So unfortunately, that means they take the CYA (cover your ass) approach and they check all of them. Now, not only have I seen this with alerts but also with things like security configurations as well. My advice is to always in to take a second and research what each option is before you check the little boxes, especially when it comes to security. Always follow the rule of less is more. In…
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OK So, I am doing some digging and peaking around again in SQL Server and came across a database option called Date Correlation Optimization Enabled = False. Honestly, I had no clue what it did, so I took it as a learning opportunity to look into it and do a little research. Who knows, it may actual help me solve one of the many problems I run into day to day for clients. Syntax ALTER DATABASE DEMO SET DATE_CORRELATION_OPTIMIZATION ON; So, What Does It Do? According to MSDN – The DATE_CORRELATION_OPTIMIZATION database SET option improves the performance of queries that perform an equi-join between two tables whose date or datetime columns are correlated,…
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Ever wander around SQL Server properties and wonder what these little check boxes turn on? I do, and I get very tempted to check them. Here is one of those tempting little boxes that seems pretty handy, Use query governor to prevent long running queries. Syntax EXEC sp_configure 'show advanced options', 1; GO RECONFIGURE ; GO EXEC sp_configure 'query governor cost limit', 180; GO RECONFIGURE; GO How Does it Work? It’s simple. This option, available in SQL Server 2008 standard and forward, will prevent long running queries based on run time measured in seconds. If I specify a value of 180 the query governor will not allow any execution of…
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Please, please, please Admins do not leave your default index fill factor at 0. This means you are telling SQL Server to fill the page 100% full when creating indexes. This also means you are forcing it to a new page when additional inserts are done. These are called PAGE SPLITS which can take time to perform and is a resource intensive operation. Having a high fill factor will cause more index fragmentation, decrease performance and increase IO. If you find that this is how your system is configured, all is not lost. You can correct this by changing the default value so that new indexes will be created with…
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How many of you check the amount of Virtual Log Files (VLFs) your transaction logs have? Working as a consultant now, I see this as something that is often ignored by DBAs. This is an easy thing maintain and yet so many don’t know how to. Keeping these in check can give you a performance boost not only on startup but with your insert/update/delete as well as backup/restore operations. SQL Server performs better with a smaller number of right sized virtual log files. I highly recommend you add this to your server reviews. What is a VLF? Every transaction log is composed of smaller segments called virtual log files. Every…
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I think sometimes those of us that have been doing database administration/development for a while take it for granted that everyone knows the basics. One such basic is parameterizing stored procedures. This allows us to potentially consolidate multiple stored procedures into a single procedure. It’s as simple thing to do that many don’t. I try to parameterize as many stored procedures as possible. This not only minimizes the amount of procedures I need to maintain, it in my opinion is a much cleaner way to code. It disturbs me when I see multiple stored procedures that pull the exact same data, but may have slight differences between them. Whether it…
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Wonder if I Do Things Differently? I am always wondering what other DBA’s do and if I am doing things differently. One such thing is my initial server setups, basically, what I configure for each of my new servers. So, why not blog about it and see what others chime in with after they read this. Keeping in mind that everyone has different requirements and different ways that they like to do the actual configurations. For now, I am not going to go into what each one of these configurations do and why I choose the value I do. That’s for another time. If you want that information you can…
