One of the new features in SharePoint 2010 which has not received a lot of attention is gradual site delete. This is a feature that was added to help reduce the performance impact of deleting site collections.
In SharePoint 2007 when you delete a site collection it is immediately purged from the database along with all of the content and related sites. A single site collection delete operation may touch over 35 SQL tables and could end up causing table locking. The deletion of site collections with a large amount of content or a large number of sub-sites has the potential to cause major performance degradation of the SharePoint farm during the process.
In SharePoint 2010 site collections are deleted gradually over time to reduce the performance impact on the farm. When you delete a site collection in SharePoint 2010 it does not immediately get purged from the content databases, instead only a subset of the data is removed and the rest of the content is placed into a queue for deletion. A new timer job called Gradual Site Delete will, over time, ensure that all of the content queued for deletion is removed from the content databases. This new timer job is by default scheduled to run daily but may be configured differently or can be run manually. You will find one instance of the gradual site delete timer job for each configured web application.
To find the gradual site delete timer job, open up the SharePoint 2010 central administration and click on the monitoring heading.
Under the timer jobs heading click on the review job definitions link.
You will now see a list of the timer jobs configured for SharePoint 2010. This list will be very large and spans multiple pages. You may need to click on the next page link located at the bottom of the job definition page in order to find the gradual site delete timer jobs.
Clicking on one of the gradual site delete links will give you the option to disable the job (not recommended), change the schedule or manually run the job.
A side effect of this new gradual site delete feature is that if you delete a site collection and then try to immediately restore a back-up to that same URL or if you try to create a new site collection at that URL you may receive a rather cryptic error message. To overcome this issue you need to manually run the gradual site deletion timer job for the appropriate web application after deleting the site collection. This will ensure that all of the content from the deleted site collection is purged from the databases. Once the gradual site deletion process has completed you should be able to restore or create a new site collection at the same URL.
For a more in-depth explanation of the gradual site delete function in SharePoint 2010 please see this post on Bill Baer’s blog.