For instructions on the use of

1. The diffcol task, see
http://internal.greenstone.org/wiki/About_Nightly_Crons#Diffcol
http://internal.greenstone.org/wiki/About_Nightly_Crons#Setting_up_and_running_diffcol_on_Windows
http://internal.greenstone.org/wiki/About_Nightly_Crons#Setting_up_and_running_diffcol_on_the_Mac

2. The gen-mode-colls.sh script, see
http://internal.greenstone.org/wiki/About_Nightly_Crons#Automatically_adding_new_or_rebuilding_existing_model-collections