Oracle: Online statistics gathering

Loading large amounts of data into a database might cause optimizer statistics to become stale. In the case of a create table … as select statement, there is even a new table for which there is no statistics available at all.

Therefore, after such bulk operations, the statistics of the modified objects should be updated.

With online statistic gathering, Oracle gathers optimizer statistics automatically, that is, without having to explicitly call dbms_stats for the following operations:

• Creation of an index
• Direct path insert into … as select (IAS) into empty tables

While online statistics gathering is limited to bulk operations, real-time statistics gathers data for conventional DML statements operations.