Using pre- and post-session SQL.

The preferred method for dropping and re-creating indexes is to define an SQL statement in the Pre SQL property that drops indexes before loading data to the target. Use the Post SQL property to recreate the indexes after loading data to the target. Define the Pre SQL and Post SQL properties for relational targets in the Transformations view on the Mapping tab in the session properties.

Using the Designer.

The same dialog box you use to generate and execute DDL code for table creation can drop and recreate indexes. However, this process is not automatic. Every time you run a session that modifies the target table, you need to launch the Designer and use this feature.