Suppose table A is very large and you want to create table B using create table… as select and want to speed up this activity. You can use the nologging keyword. For example:

create table Bnologgingas select * from A;

Use of nologging keyword precludes the generation of redo log entries.

Note: Since the new table’s creation is not being written to the redo log files, the table will not be re-created in case of a database failure. Therefore, you should consider taking a backup of the database soon after using the nologging option if you want to be able to recover your new table.