Many years ago, in the company I was working for, one junior DBA started a reindex operation in a SQL Server Standard Edition on the most busy day of the month. Do I need to explain what happened next? It’s easy to use the imagination on this one. What’s the option to solve this? Online … Read more
Rebuilding indexes is an activity that you shouldn’t need to do often. There are always a few special cases – like when you’ve moved or recreated a table or if you’ve done a massive delete on a table – when it’s probably a reasonable idea but, in general, there are very few cases where there’s any great benefit to b… Read more
The Oracle database has many features that are not spoken of frequently and a recent note by Connor McDonald reminded me that there are a couple of notes about optimising Text indexes that have been on my “must write” list for several years. If you’re not familiar with what text indexes can do for you, here’s a thumbnail sketch: creat… Read more
As data in tables is updated and / or deleted, pockets of empty space can be created, leading to fragmented free space. This free space is wasted space as it is insufficient to hold new data. Moreover, it can impact performance of the database as a higher number of sparsely-populated blocks need to be visited. Oracle 11g introduced online segment… Read more
In a recent article about dropping columns from a table I left hanging the question of what you might do after you have dropped the column, because dropping a column is really nothing more than a special case of the “massive delete”. In this article, then, I’m going to lay the groundwork for how we ought to think around t… Read more
SQL Server Indexes need to be effective. It is wrong to have too few or too many. The ones you create must ensure that the workload reads the data quickly with a minimum of I/O. As well as a sound knowledge of the way that relational databases work, it helps to be familiar with the Dynamic Management Objects that are there to assist with your indexing strategy.… Read more
XML Indexes make a huge difference to the speed of XML queries, as Seth Delconte explains; and demonstrates by running queries against half a million XML employee records. The execution time of a query is reduced from two seconds to being too quick to measure, purely by creating the right type of secondary index for the query.… Read more
