Row set size
We Since version 3.0, we changed the default Row Set size from 1000 to 10000. When you create a new transformation this will be put in place automatically.
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The maximum number of rows in the row sets can be changed in the Transformation settings dialog (CTRL-T keyboard shortcut): 
Please note that the excessive locking problem was examined and solved in versions >= 3.0.2.
Enabling the option "Manage Thread Priorities" will get rid of the issue in those later versions.
General Note about Performance: In a lot of cases a smaller row set size actually improves performance since it forces rows through all steps of a (parallel executing) transformation.