How does one disable Parallel Query?

Per table, execute the following DDL commands:

ALTER TABLE table_name PARALLEL (DEGREE 1 INSTANCES 1);

ALTER TABLE table_name NOPARALLEL;

ALTER INDEX index_name PARALLEL (DEGREE 1 INSTANCES 1);

ALTER INDEX IND_XXX NOPARALLEL;

You can also remove the INIT.ORA parameters that allow Parallel Query to work.