Locally/Dictionary Managed Tablespace

Tablespaces that record extent allocation in the dictionary, are called dictionary managed tablespaces, and tablespaces that record extent allocation in the tablespace header, are called locally managed tablespaces.
By declaring a tablespace as DICTIONARY managed, you are specifying that extent management for segments in this tablespace will be managed using the following dictionary tables: sys.fet$, sys.uet$
A Locally Managed Tablespace is a tablespace that manages its own extents by maintaining a bitmap in each datafile to keep track of the free or used status of blocks in that datafile. Each bit in the bitmap corresponds to a block or a group of blocks