DBCC Clonedatabase and Very Large Databases

One of the recent feature introductions to SQL Server is dbcc clonedatabase, a feature that lets you create a “data-less” clone of you database. All of the statistics and objects come into your cloned database, however none of the data does. This is perfect for development or performance tuning exercises, where you want all the metadata, but do not want the security risk of dealing with production data.

Recently I had the opportunity to use clonedatabase on a very large database. I was concerned about the size of the data files and how this would impact space on my volumes. Books Online is fairly clear, but I wanted to see for myself.

Note All files in the target database will inherit the size and growth settings from the model database. File name convention: The file names for the destination database will follow the source_file_name _underscore_random number convention. If the generated file name already exists in the destination folder, DBCC CLONEDATABASE will fail

So my thought in reading that, is that the same number of data files will be created in the clone, just with the settings in model. Let’s test that out.

The first thing I did was create a new database, and then add a few data files to it. I made them 20 MB, which is a different size than model—just for testing purposes.

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Next, I ran the clone database command.

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Then connect to the clone and look at the data files

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I can see that all of the files were created, in the same location as the files on the source database, except with the size settings of model. While this shouldn’t be a big deal for most, if you do like I recommend and make model a reasonable size for your environment, and you happen to be tight on drive space, you could fill up a volume. So just be aware when using clonedatabase particularly with databases that have a lot of data files in them.

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