When you synchronize dynamic cache with the lookup source, the Lookup transformation behavior does not change for update rows. When the Integration Service receives update rows, it updates the dynamic lookup cache and sets the value of NewLookupRow to 2. It does not update the lookup source. You can route the update rows through an Update Strategy transformation and pass the rows to the target.
When the Integration Service inserts rows into the lookup source, it sets NewLookupRow to 1. The Integration Service updates the dynamic lookup cache. When the transformation is configured to synchronize dynamic cache, and NewLookupRow is 1, you do not need to pass insert rows to the target.
When you configure the Insert Else Update property in the Lookup transformation, and the source row is an insert row, the Integration Service either inserts the row in the cache and the lookup source, or it updates the cache.
When you configure the Update Else Insert property in the Lookup transformation, and the source row is an update row, the Integration Service either updates the cache or it inserts the row into the cache and the lookup source.
When different sessions process update rows for the same table, the processing order varies. You might get unexpected results.