Enable Continuous Crawl in SharePoint 2013

Enable continuous crawls is a crawl schedule option that is new in SharePoint 2013. It is available only for content sources that use the SharePoint sites content source type. A continuous crawl starts at set intervals. The default interval is 15 minutes, but you can set continuous crawls to occur at shorter intervals by using Windows PowerShell.

Prerequisites:

• Create a Search Service Application
• Create at least one content source of type "SharePoint Sites".

Enabling Continuous Crawl:

• Go to Central Administration –> Application Management –> Manage Service Applications –> Search Service Application
• Click on Content Sources from left navigation
• Click new content source or edit an existing content source
• Under the crawl settings section, you can choose the option "Enable Continuous Crawls".
  
  Note: This option will be available to only on the content sources of type "SharePoint Sites".
• Save the changes.

Disabling Continuous Crawl:

• From the content source page, chose the option "Enable Incremental Crawls" option. This will disable the continuous crawl.
• Save changes.

Advantages:

• Search results are very accurate and very fresh as the index is updating time to time.
• Search administrators do not need to monitor for content freshness.

Things to remember:

• Even though the continuous crawl is loading fresh results, if your organization is big with huge data then the continuous crawl needs a minimum span of 2 hours.
• If the data is not changing very frequently in the SharePoint sites then it will not be the right option.
• If you are having any public web sites and need to show the real time data then consider using this option.

Changing the time span for the continuous crawl using Powershell:
As we already discussed the default span it takes is 15 minutes. Though we can modify this using the powershell scripting.
Please go through the MSDN link to understand more about Set-SPEnterpriseSearchCrawlContentSource