5-2 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)
5-3 Copyright © 2005, Oracle. All rights reserved.
Storage Structures
Database
Tablespace
Segment
Extent
Oracle datablock
Logical Physical
OSblock
OS file
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How Table Data Is Stored
Tablespace
Table A Table B
SegmentSegment
Rows
Columns
Table
Blocks
Row piece Extent
5-5 Copyright © 2005, Oracle. All rights reserved.
Anatomy of a Database Block
Block header
Free space
Row data
Growth
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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
5-7 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.
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Tablespaces in the Preconfigured Database
• SYSTEM• SYSAUX• TEMP
• UNDOTBS1• USERS• EXAMPLE
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Where We Are
• 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)
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What Is Automatic Storage Management?
• Is a portable and high-performancecluster file system
• Manages Oracle database files
• Spreads data across disksto balance load
• Mirrors data
• Solves many storage management challenges
ASM
Filesystem
Volumemanager
Application
Database
Operating system
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ASM: Key Features and Benefits
• 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
5-24 Copyright © 2005, Oracle. All rights reserved.
ASM: Concepts
Database
Tablespace
Segment
Extent
Oracle datablock
Data file
Physicalblock
ASM disk
ASM file
Allocation unitFile system
fileor
Raw device
ASMdisk group
5-25 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