We encountered an issue recently in an ETL process during the extract portion. When extracting from one very large table, using a NOLOCK hint, we were encountering errors indicating that the data was changing while we were extracting it. Since no other processes were supposed to be using the table during the same time window as the ETL, this was a source of some confusion. Since there was nothing indicating what, if anything, was changing the data, we needed a quick way to see what was going on in the database at the point the package failed.
Normally, when troubleshooting database activity problems, I’d just run sp_who or sp_who2. However, since the problem was occurring between 2 and 3 am, nobody was terribly excited around getting up to monitor the server. We didn’t really want to leave Profiler running all night either. So, we set up the package to log the current database activity whenever an error occurred. Basically, in the OnError event handler, we just added a data flow. The data flow runs the sp_who stored procedure to get the current activity on the database, and saves it to a text file.
This was pretty simple, and I’ve created a sample package to show it. The main control flow has a script task that generates an error, purely for the purpose of firing the OnError event handler.
The event handler does a check to make sure this is the first time it’s fired, since we didn’t want to log the activity multiple times. It then runs a data flow, and once it completes, sets a flag to ensure it doesn’t doesn’t fire again.
The data flow runs sp_who. While sp_who2 gives better information, it doesn’t provide metadata in an easily consumable format for SSIS. sp_who, on the other hand, works right off, so we went with it for simplicity. The output is sent to a text file.
It was pretty simple to implement, and it served the purpose. By reviewing the information logged, we could tell what other processes were running, and what computer it originated from. If you ever encounter a similar situation, hopefully this can help. The template package is located on my SkyDrive.
