Google enhances its hosted Site Search service for businesses (formerly Google Custom Search Business Edition) by rolling out “On-Demand Indexing” that gives site owners full control to incorporate new pages and updates into search results on their website.
On-Demand indexing allows anyone with a Google Custom Search Engine or Google Site Search to identify and tell us about new pages or recent site changes by submitting a Sitemap to our Webmaster Tools. You can then select this specific Sitemap in the Indexing tab of your CSE control panel and hit the new "Index Now" button. We will immediately schedule the relevant pages for crawling and indexing, and these pages will be included in your search results usually within 24 hours - often much faster.
We realize that new or frequently updated content is often crucial to a website. In order to give you more control over how you use the On-Demand Index resources allocated to you, we will honor the priority and lastmod attributes that you provide in your Sitemap - this means you can identify what URLs should be given preference. Please ensure that your Sitemap metadata is up-to-date.
On-Demand Indexing uses a special index that is designed just for Custom Search. The main Google search indexing process is separate and uses different selection criteria. [Google CSE Blog]
Google Site Search builds on the Google Custom Search Engine by adding business integration features, the option to turn off ads, a more customized look and feel, as well as email and phone support. Anyone with a website can take advantage of On-Demand Indexing today by signing up for Google Site Search.
Check out this video to learn more:
More info: Google Site Search