This issue is found in SharePoint platforms having large list and libraries with more than recommended number of items. From Crawl log one can find out below exception if queried as: sts3s://<<WebApplication>>/contentDbid
An unrecognized HTTP response was received when attempting to crawl this item. Verify whether the item can be accessed using your browser. (HttpStatusCode Found The request failed with the error message: -- <html><head><title>Object moved</title></head><body> <h2>Object moved to <a href="<<WebApplication>>//_layouts/1033/error.aspx?ErrorText=Request%20timed%20out%2E">here</a>.</h2> </body></html> --.)
The un-crawled contents anyway get crawled if Full Crawl runs, however it is not practically possible to run Full Crawl on daily basis in a large farm.
Hence below approach can be taken to increase the time out setting of the crawler by which the items which normally get missed out of incremental crawl because of high time taken can be crawled successfully.
Now the items which were not crawled will be crawled in Incremental crawl and the issue will be resolved.
Patris_70 edited Revision 2. Comment: deleted (en-US) title
Richard Mueller edited Revision 3. Comment: Modify title
Craig Lussier edited Revision 1. Comment: added en-US to tags and title