A table of a statement marked as NOLOGGING will bypass the Oracle Database - Redo Log (Transaction Log Files) generation.
Just setting a table to NOLOGGING does not mean that all redo is prevented against this table.
Only certain, Data Processing - (Batch|Bulk) Processing operation, such as direct path insert, will not be logged in the normal fashion. All other operation such as insert, update, delete and merge, will be logged as normal.
alter table big_table nologging;