This parameter was introduced by Oracle in Release 11g. It can be a powerfull tool to audit, without audit command, all the ddl language what is used into the database.
Put it on with the next command;
alter system set enable_ddl_logging=true;
For disable it, set the parameter to false;
alter system set enable_ddl_logging=false;
In Oracle 11g it logging the output to the alert.log of the database. In Oracle 12c it change and log the output to a specific file;
HTH – Antonio NAVARRO