Schema Objects in Oracle

A schema is a collection of logical structures of data, or schema objects.

·        Each user has its own single schema.

·        A schema is owned by a DB user and has the name same as that of a user.

·        Schema object can be created and manipulated with SQL

Schema objects include the following types of objects:

·        Clusters,

·        Database links,

·        Database triggers,

·        Dimensions,

·        External procedure libraries,

·        Indexes and index types,

·        External procedure libraries,

·        Indexes and index types,

·        Java classes, Java resources and Java sources,

·        Materialized views and materialized views logs,

·        Object tables, Object types, and object views,

·        Operators, Sequences,

·        Stored Functions, procedures, and packages,

·        synonyms,

·        Tables and index organized tables,

·        Views.

There are also other types of objects which are stored and manipulated by SQL but are not Schema objects. They are:

·        Context,

·        Directories,

·        Profiles,

·        Roles,

·        Tablespaces,

·        Users

Schema objects are logical storage structures. Emphasize on logical so they don’t have a one-to-one relation to physical files stored on disk. So what this oracle does, it stores a schema object logically within a tablespace of the DB.

There are various datafiles of the tablespaces. So the data of each schema object is physically contained in one or more of these datafiles.

For Schema objects such as Clusters, Tables and Indexes we can specify how much disk space Oracle allocates for the Object within the tablespace’s datafiles.