Promotions can
rapidly cause major problems when they overlap, as it creates many
more possible options as to what rules should be applied.
For
example, if you have a buy two 'A' and get 'B' free
in a store that also has buy two 'A' and get 'C' free,
you are effectively giving both B and C away when the user buys two
of 'A'. Other problems can occur when one of the 'free' items (B or
C) in the case of the above, also earns some promotion discount. For
example, if you had another promotion buy B get D free,
then the item B (which is free thanks to one of the promotions above)
also results in a free item 'D'. So the purchase of two 'A' now gives
B, C and D for free. Probably not was intended when each promotion
was created.
To
limit the chance of multiple promotions, stores may wish to limit the
total number of promotions that can be triggered in a single order.
The config setting frontend.promotions.maximum
can be set to zero for 'no limit', or any number above to limit
promotions.