One of the essential tasks of the Oracle Database is to store data. the subsequent section briefly describes the physical and logical storage structure of an Oracle Database.

Physical storage structures

The physical storage structures are simply files that store data. once you execute a CREATE DATABASE statement to make a replacement database, Oracle creates the subsequent files:

Data files: data files contain real data, e.g., sales order and customer data. the data of logical database structures like tables and indexes are physically stored within the data files.
Control files: every database features a control file that contains metadata. The metadata describes the body of the database including the database name and therefore the locations of knowledge files.
Online redo log files: every database has a web redo log that consists of two or more online redo log files. a web redo log is formed from redo entries that record all changes made to the data .

Besides these files, an Oracle database includes other important files like parameter files, network files, backup files, and archived redo log files for backup and recovery.

Logical Storage Structures

Oracle Database uses a logical storage structure for fine-grained control of disc space usage. the subsequent are logical storage structures in an Oracle Database:

Data blocks: a knowledge block corresponds to variety of bytes on the disk. Oracle stores data in data blocks. Data blocks also are mentioned as logical blocks, Oracle blocks or pages.
Extents: An extent may be a specific number of logically contiguous data blocks wont to store the actual sort of datarmation.
Segments: a segment may be a set of extents allocated for storing database objects, e.g., a table or an index.
Tablespaces: a database is split into logical storage units called tablespaces. A tablespace may be a logical container for a segment. Each tablespace consists of a minimum of one file .

The following picture illustrates segments, extents and data blocks within a tablespace:

And the next figure shows the connection between logical and physical storage structures:

Oracle Database Architecture

Database and Instance

An Oracle Database consists of a database and a minimum of one instance.

An instance, or database instance, is that the combination of memory and processes that are a neighborhood of a running installation and a database may be a set of files that store data.

The following picture illustrates the Oracle Database server architecture.

Sometimes, a database instance is mentioned as a whole running database. However, it’s important to know the distinctions between the 2 .

First, you’ll start a database instance without having it accessing any database files. this is often how you create a database, starting an instance first and creating the database from within the instance.

Second, an instance can access just one database at a time. once you start an instance, subsequent step is to mount that instance to a database. And an instance can mount just one database at one point in time.

Third, multiple database instances can access an equivalent database. during a clustering environment, many instances on several servers can access a central database to enable high availability and scalability.

Finally, a database can exist without an instance. However, it might be unusable because it’s just a group of files.

So, this brings us to the end of blog. This Tecklearn ‘Overview of Oracle Database and its Architecture’ blog helps you with commonly asked questions if you are looking out for a job in Oracle DB. If you wish to learn Oracle DB and build a career in Database domain, then check out our interactive, Oracle 12c DBA Training, that comes with 24*7 support to guide you throughout your learning period. Please find the link for course details:

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What you will Learn in this Course?

Introduction to Oracle Database

What is the Oracle Database?
Pre-requisites for oracle database
Oracle database 12c installation
Multi-tenant architecture

Exploring the Oracle 12c Database Architecture

Explain the Memory Structures
Describe the Process Structures
Overview of Storage Structures

Preparing the Database Environment

Identify the tools for Administering an Oracle Database
Plan an Oracle Database Installation
Install the Oracle Software by using Oracle Universal Installer (OUI)
Create a Database by using the Database Configuration Assistant (DBCA)

Managing the Oracle Instance

Setting database initialization parameters
Describe the stages of database startup and shutdown

Database Storage Structures and Schema Objects

Managing Database Storage Structures
Overview of table space and data files
Overview of Primary Components
Identify the importance of checkpoints, redo log files, and archived log files
Configure ARHIVELOG mode

Database Startup & User Requests and Oracle Network Environment

Describe the stages of database startup and shutdown
Using alert log and trace files
Configure and Manage the Oracle Network
pFile and spFile
Tablespace Management
Storage and Relationship Structure

Oracle Backup & Recovery

Redo log File Management
Performing Database Recovery
Overview of Data Recovery Advisor
Use Data Recovery Advisor to Perform recovery (Control file, Redo log file and Data file)

Deep Dive into Oracle Recovery Manager (RMAN)

Using the RMAN Recovery Catalog
Identify situations that require RMAN recovery catalog
Create and configure a recovery catalog
Synchronize the recovery catalog
Create and Use RMAN stored scripts
Back up the recovery catalog
Create and use a virtual private catalog

Configuring Backup Specifications

Using RMAN to Create Backups
Create image file backups
Create a whole database backup
Enable fast incremental backup
Using RMAN to Perform Recovery
Perform complete recovery from a critical or noncritical data file loss using RMAN
Perform incomplete recovery using RMAN

Data Movement and Oracle Data Pump

Moving Data
Describe and use methods to use move data (Directory objects, SQL* Loader, External tables)
Explain the general architecture of Oracle Data Pump

Data Dictionary & Dynamic Performance Tables

Oracle Data Dictionary contains information related to database privileges
Data dictionary views
Media failure
Flashback CDB

Database Tuning

What is database tuning
How to tune the database
Tuning the data dictionary

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