When the Integration Service processes a sorted Joiner transformation, it blocks data based on the mapping configuration. Blocking logic is possible if master and detail input to the Joiner transformation originate from different sources.
The Integration Service uses blocking logic to process the Joiner transformation if it can do so without blocking all sources in a target load order group simultaneously. Otherwise, it does not use blocking logic. Instead, it stores more rows in the cache.
When the Integration Service can use blocking logic to process the Joiner transformation, it stores fewer rows in the cache, increasing performance.