n is either 1 or 0. The default value is 1.
When DDLUseExtentSet is enabled (n = 1), a table created by a DDL CREATE TABLE statement stores its index data in globals that use hashed names. The hashed names typically allow for better performance when running queries against the table, but are less comprehensible to the user. When this parameter is not enabled, the index data is stored in globals named after the class.