One of the things that we keep thinking about with RavenDB is how to make it easier for you to run in production.

To that end, we introduce a new feature in 2.5, Index Locking. This looks like this:

But what does this mean, to lock an index?

Well, let us consider a production system, in which you have the following index:

from u in docs.Users
select new
{
   Query = new[] { u.Name, u.Email, u.Email.Split('@') }
}

After you go to production, you realize that you actually needed to also include the FullName in the search queries as well. You can, obviously, do a full deployment from scratch, but it is generally so much easier to just fix the index definition on the production server, update the index definition on the codebase, and wait for the next deploy for them to match.

This works, except that in many cases, RavenDB applications call IndexCreation.CreateIndexes() on start up. Which means that on the next startup of your application, the change you just did will be reverted. These options allows you to lock an index for changes, either in such a way that gives you the ability ignore changes to this index, or by raising an error when someone tries to modify the index

It is important to note that this is not a security feature, you can at any time unlock the index. This is there to make help operations, that is all.