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Primary Note: Overview of Oracle Segment Storage (Doc ID 1491960.1)

Last updated on JUNE 13, 2023

Applies to:

Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Cloud Exadata Service - Version N/A and later
Oracle Database Backup Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Oracle Database Cloud Service - Version N/A and later
Information in this document applies to any platform.

NOTE: In the images and/or the document content below, the user information and environment data used
represents fictitious data from the Oracle sample or bulit-in schema(s), Public Documentation delivered
with an Oracle database product or other training material. Any similarity to actual environments,
actual persons, living or dead, is purely coincidental and not intended in any manner.


Oracle Segment Storage lets you specify how Oracle Database should store a database object. Storage parameters affect both how long it takes to access data stored in the database and how efficiently space in the database is used.
Database space management has always been an important part of any database administrator's job. Administrators spend a significant amount of their time planning and monitoring the space utilization in order to ensure uninterrupted database operations. In this note we are covering the segment storage parameters.


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In this Document
 Oracle Segment Concept
 Introduction to Logical Storage Structures
 Storage - Blocks, Extents, Segments
 Overview of Segments
 Logical Space Management
 Locally Managed Tablespaces
 Dictionary-Managed Tablespaces
 Segment Space Management
 Automatic Segment Space Management
 Manual Segment Space Management
 Overview of Extents
 Allocation of Extents
 Autoallocate vs. Uniform
 Deallocation of Extents
 Storage Parameters for Extents
 Segment Storage Clause
 LOB Storage Characteristics for LOB Column or Attribute
 Understand Deferred Segment Creation 
 Space Management Coordinator
 Segment Space and the High Water Mark
 Knowledge Base Notes
 How To

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