If you have more than one server supporting search collections, this dialog prompts you to specify the server collection(s) to optimize once you select Optimize Search Collection from the Site Administration left panel. Pick one or more and click Continue to complete the optimization.
Site administrators can centrally manage this function for multiple subsites through Manage Search Collections.
Related Links
You can download PDF versions of the Content Contributor's, Administrator's, and Elements Reference documents from the support section of paperthin.com (requires login).
For technical support: