What Are the Best Performance Tuning Strategies for Your SQL Server Indexes?

An optimized approach to indexing is important if you are keen to keep the performance of an SQL Server instance at its best and, in turn ,deliver a consistent experience for end users of any software solution that relies on it.

This is an easy thing to say but harder to achieve in practice unless you have the right strategies and solutions at your disposal as an administrator.

With that in mind, let’s go over some of the best tools and tactics to put to work as you aim to tune and improve the performance of your SQL Server indexes.

Weeding Out Fragmentation and Dealing With It Appropriately

The lynchpin of good SQL Server index analysis is looking into the levels of fragmentation that have developed over time and working out what type of action you need to take to remedy this.

Fragmentation is a natural occurrence in indexes, as when changes are made to the table, this means that they are not as accurate, and so it can take longer for queries to be processed if this is left unchecked.

There are two key routes to take here, one of which is reorganization, and the other is a total index rebuild.

As you’d expect, a reorganization of an index is better for lower levels of fragmentation, while a rebuild might be needed if it has become especially fragmented. The latter option is more disruptive to server performance while it is taking place, so obviously, this needs to be scheduled to avoid coinciding with peak periods of usage.

Different admins have different approaches and parameters for determining if a reorganization or a rebuild of an index is on the cards, so there is no hard and fast rule you need to adhere to. 

However, best practices state that if fragmentation is under 30 percent, you can just reorganize the index to tune performance positively, while if it is over this upper limit, rebuilding will be better.

With the right SQL Server monitoring tools to hand, you can easily stay on top of the issue of index fragmentation, and even automate the reorganizing or rebuilding of indexes when specific situations arise, or simply rely on alerts to track this and implement action on-the-fly as and when necessary.

Considering the Number of Indexes Used

Generally speaking, the presence of an index on an SQL Server table is able to enhance performance by allowing queries to get at the entry they need without having to scour the entire thing each time they are executed.

You will usually choose to add multiple indexes to a table, with a view to catering to specific types of queries that are commonly fielded. This is a good way to further optimize performance and is probably something you are already doing.

However, a couple of considerations need to be taken into account when looking into the number of indexes that are in use. First, the issue of how frequently the table is updated or altered in any way, and second, the question of the size and scale of the table.

For tables that are most often accessed, it is potentially more optimal to have a smaller number of indexes in play at any given time, because each additional layer you add can mean that queries have to jump through more hoops to execute. 

Conversely, for tables that are accessed more sporadically, you can afford to have a greater number of more specialized indexes put in place, each of which is tuned to cover a particular query that you know will make use of it at some point.

As mentioned, size also matters, and while large tables are definitely more performant if they have indexes attached, an index can actually be a speed bump in the case that a table is only populated with a very small volume of entries.

Once again, you need to look at the specific needs of your SQL Server and the types of apps that rely on it to determine the best course of action here. There is no point in assuming that the way you are doing things now is adequate because even small optimizations to your indexing strategies can deliver big benefits.

Good Query Writing Goes Hand in Hand With Index Optimization

No matter how carefully you implement and monitor SQL Server indexes, you can still expect performance to be suboptimal if you are not also up to speed with the best practices for writing queries.

Whether your queries are flabby and contain too many components and instructions or imprecise and include more table entries than is strictly necessary, going back to basics and reviewing this will also give you an insight into whether or not your indexes are also being harnessed in the right way.

From this, you will further be able to determine if the indexes you pick are aligned with the operations they will need to handle from moment to moment. They might be geared towards one type of query but create a stumbling block for another.

It is a little like needing to see both the micro and macro at once, appreciating that changing separate parts of the SQL Server setup can have a knock-on effect elsewhere, whether in terms of bolstering performance or hampering it.

Flexibility and Vigilance Are Your Friends

We have discussed that you need to look into what is best for your SQL Server in terms of index optimization and query writing, but that doesn’t mean you should rigidly follow a path you believe to be correct in the face of evidence to the contrary.

Since you can monitor your server persistently and track how performance changes over time, you can use this information to analyze and rank any changes you make, which in turn should tell you if you need to adjust further or if you are on the right track.

Being flexible and willing to change, as well as being vigilant to performance issues, will let you extract optimal performance from your SQL Server more often than not.