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9
Copyright © Oracle Corporation, 2002. All rights reserved.
Storage Structure and Relationships
9-2
Copyright © Oracle Corporation, 2002. All rights reserved.
Objectives
After completing this lesson, you should be able to do
the following:
•
Describe the logical structure of the database
•
List the segment types and their uses
•
List the keywords that control block space usage
•
Obtain storage structure information
9-3
Copyright © Oracle Corporation, 2002. All rights reserved.
Storage and Relationship Structure
Database
PROD
DISK1/SYS1.dbf
DISK2/
USER1.dbf
DISK3/
USER2.dbf
DISK1/
UNDO1.dbf
DISK1/
TEMP.dbf
D.D.
Table
Data
Seg
D.D.
Index
Index
Seg
RB
Seg
S_DEPT
Data
Seg
S_EMP
Data
Seg
Temp
Temp
Seg
1 2 1 2 1 2 1 1 2 2 1 FREE 1 1 2 2 1
EXTENTS
S_DEPT
(cont'd)
Data
Seg
S_EMP
FIRST_N
AME
Index
Index
Seg
Oracle DATA BLOCKS
RBS1
(cont'd)
RB
Seg
RBS2
(cont'd)
RB
Seg
RBS1
RB
Seg
RBS2
RB
Seg
SEGMENTS
SYSTEM USER_DATA RBS TEMP
TABLESPACES
DATA FILES
9-4
Copyright © Oracle Corporation, 2002. All rights reserved.
Types of Segments
Table
Cluster
Table
partition
Index
9-6
Copyright © Oracle Corporation, 2002. All rights reserved.
Types of Segments
Index-organized
table
Index
partition
Undo
segment
Temporary
segment
9-7
Copyright © Oracle Corporation, 2002. All rights reserved.
Types of Segments
LOB
segmen
t
Bootstrap
segment
Nested
table
9-8
Copyright © Oracle Corporation, 2002. All rights reserved.
Storage Clause Precedence
Oracle default
Tablespace
Segment
9-9
Copyright © Oracle Corporation, 2002. All rights reserved.
Extent Allocation and Deallocation
•
An extent is a chunk of space used by a segment
within a tablespace.
•
An extent is allocated when the segment is:
–
Created
–
Extended
–
Altered
•
An extent is deallocated when the segment is:
–
Dropped
–
Altered
–
Truncated
9-10
Copyright © Oracle Corporation, 2002. All rights reserved.
Used and Free Extents
Data file
Free extentUsed extentFile header
9-11
Copyright © Oracle Corporation, 2002. All rights reserved.
Database Block
•
Minimum unit of I/O
•
Consists of one or more operating system blocks
•
Set at tablespace creation
•
DB_BLOCK_SIZE is the default block size
[...]... database can be created with a standard block size and up to four nonstandard block sizes • Block sizes can have any power-of-two value between 2 KB and 32 KB 9-12 Copyright © Oracle Corporation, 2002 All rights reserved Standard Block Size • Set at database creation using the DB_BLOCK_SIZE parameter; cannot be changed without re-creating the database • Used for SYSTEM and TEMPORARY tablespaces • DB_CACHE_SIZE... information stored in the segment • Determine extent sizes using the storage clause • Control block space utilization • Obtain storage structure information 9-32 Copyright © Oracle Corporation, 2002 All rights reserved Practice 9 Overview This practice covers identifying and obtaining information on the various types of storage structures in the database 9-33 Copyright © Oracle Corporation, 2002 All... 8 KB blocks DB_16K_CACHE_SIZE for 16 KB blocks DB_32K_CACHE_SIZE for 32 KB blocks • DB_nK_CACHE_SIZE is not allowed if nK is the standard block size • Minimum size for each cache is one granule 9-15 Copyright © Oracle Corporation, 2002 All rights reserved Creating Nonstandard Block Size Tablespaces CREATE TABLESPACE tbs_1 DATAFILE 'tbs_1.dbf' SIZE 10M BLOCKSIZE 4K; DESCRIBE dba_tablespaces Name Null?... must reside in tablespaces of the same block size • All temporary tablespaces, including the permanent ones that are being used as default temporary tablespaces, must be of standard block size • Index-organized table overflow and out-of-line LOB segments can be stored in a tablespace with a block size different from the base table 9-19 Copyright © Oracle Corporation, 2002 All rights reserved Database... Usage PCTFREE=20 Inserts PCTUSED=40 80% Inserts (off freelist) 1 Inserts 2 80% 40% 3 9-28 Insert (on freelist) 4 Copyright © Oracle Corporation, 2002 All rights reserved Obtaining Storage Information Information about storage can be obtained by querying the following views: • DBA_EXTENTS • DBA_SEGMENTS • DBA_TABLESPACES • DBA_DATA_FILES • DBA_FREE_SPACE 9-29 Copyright © Oracle Corporation, 2002 All... TEMPORARY tablespaces • DB_CACHE_SIZE specifies the size of the DEFAULT buffer cache for standard block size: – Minimum size = one granule (4 MB or 16 MB) – Default value = 48 MB 9-13 Copyright © Oracle Corporation, 2002 All rights reserved 9-14 Copyright © Oracle Corporation, 2002 All rights reserved Nonstandard Block Size • Configure additional caches with the following dynamic parameters: – –... management 9-23 Copyright © Oracle Corporation, 2002 All rights reserved Automatic Segment-Space Management • It is a method of managing free space inside database segments • Tracking in-segment free and used space is done using bitmaps as opposed to using free lists • This method provides: – Ease of management – Better space utilization – Better performance for concurrent INSERT operations 9-24 Copyright . 9 Copyright © Oracle Corporation, 2002. All rights reserved. Storage Structure and Relationships 9-2 Copyright © Oracle Corporation, 2002. All rights reserved. Objectives After. following: • Describe the logical structure of the database • List the segment types and their uses • List the keywords that control block space usage • Obtain storage structure information 9-3 Copyright. Support • A database can be created with a standard block size and up to four nonstandard block sizes. • Block sizes can have any power-of-two value between 2 KB and 32 KB. 9-13 Copyright © Oracle Corporation,
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