OPTIMIZER_MAX_PERMUTATIONS restricts the number of permutations of the tables the optimizer will consider in queries with joins. Such a restriction ensures that the parse time for the query stays within acceptable limits. However, a slight risk exists that the optimizer will overlook a good plan it would otherwise have found.
The default value for this parameter is 80000, which corresponds to the no limitation at all. Setting this parameter to a value less than 1000 normally ensures parse times of a few seconds or less.
