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Managing Database Storage Structures Copyright © 2005, Oracle. All rights reserved. Objectives After completing this lesson, you should be able to do the following: • Describe how table row data is stored in blocks • Define the purpose of tablespaces and data files • Create and manage tablespaces • Obtain tablespace information • Describe the main concepts and functionality of Automatic Storage Management (ASM) 5-2 Copyright © 2005, Oracle. All rights reserved. Storage Structures Logical Physical Database Tablespace OS file Segment Extent Oracle data block 5-3 OS block Copyright © 2005, Oracle. All rights reserved. How Table Data Is Stored Columns Table A Blocks Table B Rows Segment Segment Table Tablespace Row piece 5-4 Copyright © 2005, Oracle. All rights reserved. Extent Anatomy of a Database Block Block header Growth Free space Row data 5-5 Copyright © 2005, Oracle. All rights reserved. Tablespaces and Data Files The Oracle database stores data logically in tablespaces and physically in data files. • Tablespaces: – Can belong to only one database – Consist of one or more data files – Are further divided into logical units of storage • Data files: – Can belong to only one tablespace and one database – Are a repository for schema object data Database Tablespace Data files 5-6 Copyright © 2005, Oracle. All rights reserved. Space Management in Tablespaces • Locally managed tablespace: – – – – – • Free extents are managed in the tablespace. A bitmap is used to record free extents. Each bit corresponds to a block or group of blocks. The bit value indicates free or used extents. The use of locally managed tablespaces is recommended. Dictionary-managed tablespace: – Free extents are managed by the data dictionary. – Appropriate tables are updated when extents are allocated or unallocated. – These tablespaces are supported only for backward compatibility. 5-7 Copyright © 2005, Oracle. All rights reserved. Creating a New Tablespace 5-8 Copyright © 2005, Oracle. All rights reserved. Storage for Locally Managed Tablespaces 5-10 Copyright © 2005, Oracle. All rights reserved. Tablespaces in the Preconfigured Database • • • 5-12 SYSTEM SYSAUX TEMP • • • UNDOTBS1 USERS EXAMPLE Copyright © 2005, Oracle. All rights reserved. Altering a Tablespace 5-14 Copyright © 2005, Oracle. All rights reserved. Actions with Tablespaces 5-17 Copyright © 2005, Oracle. All rights reserved. Dropping Tablespaces 5-19 Copyright © 2005, Oracle. All rights reserved. Viewing Tablespace Information 5-20 Copyright © 2005, Oracle. All rights reserved. Where We Are • • • • • 5-21 Using tablespaces to separate data Creating various types of tablespaces Managing tablespaces Obtaining tablespace information Describe the main concepts and functionality of Automatic Storage Management (ASM) Copyright © 2005, Oracle. All rights reserved. What Is Automatic Storage Management? • • • • • Is a portable and high-performance cluster file system Manages Oracle database files Application Spreads data across disks to balance load Database Mirrors data File system Solves many storage ASM Volume management challenges manager Operating system 5-22 Copyright © 2005, Oracle. All rights reserved. ASM: Key Features and Benefits • • • • • • • 5-23 Stripes files, but not logical volumes Provides online disk reconfiguration and dynamic rebalancing Allows for adjustable rebalancing speed Provides redundancy on a per-file basis Supports only Oracle database files Is cluster aware Is automatically installed Copyright © 2005, Oracle. All rights reserved. ASM: Concepts ASM disk group Database Tablespace ASM file Data file Segment Extent Oracle data block 5-24 ASM disk File system file or Raw device Allocation unit Physical block Copyright © 2005, Oracle. All rights reserved. Summary In this lesson, you should have learned how to: • Describe how table row data is stored in blocks • Define the purpose of tablespaces and data files • Create and manage tablespaces • Obtain tablespace information • Describe the main concepts and functionality of ASM, such as: – Disk mirroring – Dynamic rebalancing – ASM disk groups 5-25 Copyright © 2005, Oracle. All rights reserved. Practice Overview: Managing Database Storage Structures This practice covers the following topics: • Creating tablespaces • Gathering information about tablespaces 5-26 Copyright © 2005, Oracle. All rights reserved.