My name is HarshDeep Singh, and I am a SQL Server engineer with Microsoft CSS. I've been working on SQL Server for quite some time, and the intention behind starting this blog is to try and share my knowledge with the SQL Server community. Any feedback or suggestions on the blog are both welcome and solicited. Please feel free to drop me a line on firstname.lastname@example.org anytime.
It’s very rare that I run into an issue with the Resource database, and the one I ran into recently was rarer still. But before I get into the nitty-gritty of the issue, let us begin by outlining a few details about the resource database:
The Resource database
The resource database is a hidden system database, and cannot be accessed explicitly by the users. Also, as documented here, there is no way inside SQL Server to back up the resource DB. The only way to take a backup of the resource db is to make file level copies. This is something that you can do either manually or through VSS (disk level) backups.
Now, it’s not without reason that we do not have any way to take backups of the Resource database. A few salient points:
But what if there is a hardware problem, say, god forbid, your SAN crashes, or if there’s some sort of a “scribbler” issue with one of the hardware drivers (more details on that in a different post), and you end up with your resource database corrupted, what do you do? Here are the options, in order:
Now, allow me to explain why this special case described in bullet 3 exists: In SQL 2005, the resource db was tied to the master database, and the resource db mdf and ldf files had to be in the same folder as the master db files, else your SQL Service would fail to start. In case of a cluster, the resource db resided on a clustered drive, and when the failover happened, the ownership of the resource database was passed to the second node. Since we had only one copy of the resource database to patch, we were able to patch all the nodes on the cluster in a single run in case of SQL 2005.
This behaviour changed from SQL 2008 onwards. In SQL 2008 and 2008 R2, the resource database is no longer tied to the master database, and exists in the Binn folder instead. So basically, the resource database is a part of the instance binaries from SQL 2008 onwards. This is why, in case of SQL 2008 and 2008 R2, you need to patch both the nodes separately (one by one). Makes sense? This is why I mentioned in point 3 above that if you are on a cluster and SQL is 2008 or later, there is a good chance you might be able to get SQL up on the other node, even if the resource db files on one node are corrupted.
As a last word, if you’re not sure how your resource db files came to be corrupted, please take it as a top priority to find the root cause behind the corruption, as this is definitely something that warrants further investigation.
If you have any interesting incidents to share w.r.t the resource database, please feel free to do so in the comments section.