What are Extracts and Schedules in Tableau server?

An extract is a compressed snapshot of the data stored in Tableau's own columnar format rather than queried live from the source. It is usually much faster, works when the source is unavailable, and takes load off production systems.

A schedule is what keeps that snapshot current. Extracts do not update themselves, so on Server you attach a refresh schedule at whatever cadence the data warrants.

Refreshes come in two forms. A full refresh rebuilds the whole extract. An incremental refresh appends only rows where a chosen column — usually a timestamp or an ID — exceeds the highest value already present.

Incremental is far cheaper but blind to rows that were updated or deleted after the fact, so a common pattern is incremental nightly with a full refresh weekly.