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Oracle object namespaces

All objects Within a given object namespace must be identified by a unique name.

In a schema, the following objects share the same namespace:

Tables
Views
PL/SQL units (Packages, stand alone procedures and functions, user-defined types and operators)
Private synonyms
MLE objects (?)

On the other hand, each object-type of the following list has an independent namespace within a given schema:

Indexes
Triggers
Constraints
Materialized views
Clusters
Dimensions
Private database links

Each of the following non-schema objects also have an independent namespace:

Tablespaces with tablespace groups.
User roles
Public synonyms
Editions
Parameter files (pfiles) and server parameter files (spfiles)
Profiles
Public database links

Because of these namespaces, it's possible to create multiple objects with the same name:

create table           tq84_a_name  (a number, b varchar2(10), c date);
alter  table           tq84_a_name   add constraint tq84_a_name primary key(a);
create cluster         tq84_a_name  (a number(4)) hash is a hashkeys 8192;
create public synonym  tq84_a_name   for sys.dual;
create index           tq84_a_name   on tq84_a_name (b);

Oracle object namespaces

See also