What is an unused managed property in SharePoint 2013 search?

Question

In quite a few pages on Microsoft TechNet describing the new search schemas for SharePoint 2013, they use the phrase, unused managed property. It's not entirely clear what that means in this context. If tenants and site collections can have their own search schemas now, does that not allow for their own definitions of managed properties? Does each property name have to be unique across all schemas?

Reference

• Manage the search schema in SharePoint Server 2013, TechNet, SharePoint 2013, Published: July 16, 2012
• Introducing Search Schema for SharePoint 2013, TechNet Blogs, SharePoint IT Pro Blog, 25 Nov 2012 11:23 PM
• SharePoint Search 2013: Why are there so many Managed Properties?, TechNet Blogs, Helge Solheim, 29 Nov 2012 6:01 AM

Answer 1

At the bottom of Manage the search schema in SharePoint Server 2013, it describes the use of these "unused managed properties". It states:

The following table provides an overview of the default unused managed properties that you can reuse and rename using an Alias.

and continues with a table of managed properties that are shipped OOTB, but that are not used in the 600 some odd managed properties.

Even though multi-tenancy environments now have their own search settings, you are unable to create a new managed property (or perhaps only certain types? I don't have the ability to confirm this). Instead the "unused managed properties" can be repurposed as search schemas in a multi-tenancy environment.

Helge Solheim describes this in his blog post that you linked:

4) The new multiple index schema mechanism with index schemas on tenant and site collection level (covered by the other blog post). To accomodate this without making things too expensive these additional schemas cannot create "expensive managed properties". However, they can reuse existing managed properties, and we ship with a number of default unused managed properties named RefinableString22 etc. There are 270 of these managed properties in total, if I managed to get the math right.

So MSFT provides these pre-configured "unused managed properties" for this purpose.

Hope this helps.