Microsoft Sharepoint Products and Technologies Resource Kit eBook

Chapter 21: The Architecture of the Gatherer 601
If no other updates have been performed, the first time an adaptive update is
performed is equal to performing a full update. The second time an adaptive update
is performed is equal to performing an incremental update. Because of this, performance
improvements are not seen until the third time an adaptive update is
performed.
Safeguards for Adaptive Updates
An adaptive update is faster than an incremental or full update, but there is a chance
that an adaptive update could miss some updated content. Adaptive updates check
only content that is likely to have changed, so if a document does not change often
it might be overlooked by adaptive updates. To account for this, SharePoint Portal
Server places a two-week maximum between crawls on documents. This is a safeguard
to ensure that all changes get included in the index.
You should not use adaptive updates if having a fully accurate index is important
in your environment. This recommendation is given because adaptive updates
are never 100 percent accurate in crawling all the modified content. Instead, adaptive
updates only crawl that content that the algorithm predicts is most likely to have
changed. A document that is seldom modified might not have its changes appear for
up to two weeks in the index. You must consider the advantages of using the adaptive
update performance features against the potential delay of getting updated
information into the index.
Frequency of Updates
By default, when SharePoint Portal Server is installed, four updates are scheduled to
run. These updates are as follows:
■ An incremental update of portal site content that occurs every 10 minutes
■ An incremental update of the people content source that occurs every hour
■ An incremental (inclusive) update of portal site content that occurs once a night
■ An incremental update of nonportal site content that occurs once a night
In general, an update schedule should be based on how quickly new content
needs to be available for searches or alerts. This need must be balanced against the
resources and time required to crawl content.
Starting an Update
An update can be started only if the update status is Idle. The update status for a
content index is in the Update Status column on the Configure Search And Indexing
page on the SharePoint Portal Server Central Administration page. For the content
source, the update status can be viewed in the Update Status column on the Manage
Content Sources page.