What are the components of physical database structure of Oracle database?
- Data Files: These are the actual files where the data is stored. They hold tables, indexes, clusters, and other database objects.
- Control Files: These files are crucial for database operation as they contain metadata about the physical structure of the database and ensure consistency and integrity.
- Redo Log Files: These files store a record of changes made to the database. They help in recovery and rollback operations in case of failures.
- Tablespaces: They are logical storage units made up of data files. Tables and indexes are stored within tablespaces.
- Segments: These are portions of a tablespace that physically hold data. They include data segments for tables and indexes, rollback segments, and temporary segments.
- Extent: Extents are units of database space allocation made up of a specific number of contiguous data blocks. When a segment needs more space, it is allocated in extents.
- Data Blocks: These are the smallest unit of data storage in an Oracle database. All the database’s data is stored in these blocks.
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What are the components of logical database structure in Oracle database?
The logical database structure in an Oracle database includes several components that primarily organize and manage data conceptually:
- Tablespaces: These are logical storage containers for organizing and grouping related database objects. Tables, indexes, and other data structures are stored within tablespaces.
- Schema: A schema is a collection of database objects (tables, views, indexes, etc.) owned by a specific database user. It provides a way to organize and manage objects within the database.
- Tables: Tables are the fundamental storage structure in a database, holding data in rows and columns.
- Indexes: Indexes are structures that enhance data retrieval by providing quick access to rows in a table based on the values of certain columns.
- Views: Views are virtual tables derived from one or more tables. They present data in a way that can simplify complex queries and provide a layer of abstraction over the actual data.
- Constraints: Constraints enforce rules and restrictions on the data stored in tables, ensuring data integrity. Examples include primary key, foreign key, unique, and check constraints.
- Synonyms: Synonyms are aliases for database objects, simplifying access to those objects and providing a level of abstraction.
- Sequences: Sequences are objects used to generate unique numeric values, often for primary key generation.