Storage Structure and Relationships pdf

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,