A useful undocumented function: fn_dblog

A useful undocumented function: fn_dblog:
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A useful undocumented function: fn_dblog
Posted by decipherinfosys on November 12, 2008

A friend of mine recently told me about this undocumented function: ::fn_dblog when I was talking to him about Lumigent’s Log Explorer product. He pointed me to this post by Andrew Novick which mentions about this function which has existed since quite some time. I have always been using DBCC SQLPERF(LogSpace) when I wanted to capture used and free space and at times DBCC LOGINFO with help from different sites out there to understand the output. I am a fan of Lumigent’s product and have used it quite a bit in our client engagements but the fact that something like this existed all along, was a welcome surprise to me so I thought that we would share this on the blog with our readers as well.

As the post from Andrew Novick points out, the syntax is :

::fn_dblog(@StartingLSN, @EndingLSN)And if you provide Null as the value for both the parameters, then you will get a running record of everything from the start to the end (not a good idea in a production environment but something to play around with in your development/test environment to get an understanding of the output). The post from Andrew goes into some of the details of what the different columns are for.