3 Copyright © 2004, Oracle. All rights reserved. Database Architecture Comparison

3-2 Copyright © 2004, Oracle. All rights reserved. Objectives After completing this lesson, you should be able to do the following: Compare SQL Server and Oracle database concepts at a high level Explore the Oracle Database 10g architecture Use the Database Configuration Assistant to create an additional database

3-3 Copyright © 2004, Oracle. All rights reserved. What Is a Database? Oracle database: Collection of schemas Stored in tablespaces Central schema: SYS SQL Server database = Oracle schema Memory Processes SYS SYSTEM Tablespace 1 Tablespace 2 Tablespace 3 Memory Processes Master, model,msdb, tempdb Database 1 Database 2 Database 3 Oracle instance = SQL Server server (Database plus processes)

3-4 Copyright © 2004, Oracle. All rights reserved. Comparing Oracle and SQL Server Connections Oracle: connect to schema SQL Server:connect to database ODBC Native connection

3-5 Copyright © 2004, Oracle. All rights reserved. Differences in Connection Models The Oracle server is “connection-based.” It offers: –Multiple active result-sets per connection –The need for only one connection –Multiple sessions per connection –Multiple transactions per session –Distributed database access via database links SQL Server is “stream-based.” It offers: –One active result-set per connection –Sequentially multiple result-sets –Typically, the need for several connections

3-6 Copyright © 2004, Oracle. All rights reserved. Comparing Transactional Models OracleSQL Server Readers never block writers. Readers may block writers. Read transactions are always consistent. “Dirty reads,” that is reads of uncommitted data, are allowed. Writers never block readers. Writers can block readers, unless readers use dirty data. Writers wait on writers for identical rows only. Writers wait on writers at row/page level. Locks are stored with the data. Locks are stored in memory.

3-7 Copyright © 2004, Oracle. All rights reserved. Comparing Storage Structures Oracle Database Tablespace Segment Extent Block SQL Server Database Filegroup Extent (64 KB fixed) Page (8 KB fixed)

3-8 Copyright © 2004, Oracle. All rights reserved. SQL Server Storage Structures Fundamental storage unit: Page (8 KB fixed) Basic unit to allocate space to tables and indexes: Extent (64 KB fixed) OS file: Primary data file Secondary data file Database Log file Filegroup

3-9 Copyright © 2004, Oracle. All rights reserved. Oracle Storage Structures Fundamental storage unit: Block A logical block consists of one or more OS blocks. The size of a logical block is defined by the initialization parameter. OS block Tablespace LogicalPhysical Extent Segment Block Data file

3-10 Copyright © 2004, Oracle. All rights reserved. What Did You Learn So Far? Mark each of the following statements about an Oracle database as True or False: 1.A database can have only one active result-set per connection. 2.Transaction locks can never escalate. 3.Read transactions always use locks for consistency. 4.The Oracle database uses row-level locks on data blocks. 5.The Oracle server allows reads of uncommitted “dirty” data. 6.A tablespace is a logical storage unit, implemented by using physical files. 7.The size of an Oracle database is always smaller than the sum of its tablespaces.

3-11 Copyright © 2004, Oracle. All rights reserved. Exploring Oracle’s Database Architecture Data filesOnline redo log files Password fileParameter file Archive log files Control files

3-12 Copyright © 2004, Oracle. All rights reserved. Exploring the Storage Structure Click the links to view detailed information.

3-13 Copyright © 2004, Oracle. All rights reserved. Control Files Contain physical database structure information Should be multiplexed to protect against loss Are required to access the database Control files

3-14 Copyright © 2004, Oracle. All rights reserved. Redo Log Files Record changes to the database Should be multiplexed to protect against loss Redo log buffer Log writer LGWR Group 1Group 2Group 3

3-15 Copyright © 2004, Oracle. All rights reserved. Tablespaces and Data Files Tablespaces consist of one or more data files. Data files belong to only one tablespace. USERS tablespace Data file 1 Data file 2

3-16 Copyright © 2004, Oracle. All rights reserved. Segments, Extents, and Blocks Segments exist within a tablespace. Segments are made up of a collection of extents. Extents are a collection of data blocks. Data blocks are mapped to disk blocks. SegmentExtentsData blocks Disk blocks

3-17 Copyright © 2004, Oracle. All rights reserved. Oracle Instance Management System Monitor SMON Database Writer DBWn Log Writer LGWR Process Monitor PMON Archiver ARCn SGA Java pool Shared poolLarge poolStreams pool Database buffer cache Redo log buffer Check point CKPT

3-18 Copyright © 2004, Oracle. All rights reserved. Oracle Memory Structures Java pool Database buffer cache Redo log buffer Shared pool Large pool SGA Streams pool Server process 1 PGA Server process 2 PGA Back- ground process PGA

3-19 Copyright © 2004, Oracle. All rights reserved. Oracle Memory Structures Full Notes Page

3-20 Copyright © 2004, Oracle. All rights reserved. Oracle Processes System Monitor SMON Database Writer DBWn Check point CKPT Log Writer LGWR Process Monitor PMON Archiver ARCn Server process Server process Server process Server process Shared Global Area SGA Background processes

3-21 Copyright © 2004, Oracle. All rights reserved. Data Dictionary

3-22 Copyright © 2004, Oracle. All rights reserved. Database Architecture Quiz Mark each of the following statements about an Oracle database as True or False : 1.Control files store information about the physical database structure. 2.Transaction changes are stored in redo log files. 3.Tablespaces consist of one or more data files. 4.A data file can be used for more than one tablespace. 5.Log Writer (LGWR) writes redo log entries to disk. 6.Database Writer (DBWn) writes modified blocks from the buffer cache to disk. 7.All Oracle background processes are optional.

3-23 Copyright © 2004, Oracle. All rights reserved. Database Configuration Assistant (DBCA): Overview

3-24 Copyright © 2004, Oracle. All rights reserved. Using the DBCA to Create a Database

3-25 Copyright © 2004, Oracle. All rights reserved. Using the DBCA to Create a Database

3-26 Copyright © 2004, Oracle. All rights reserved. Using the DBCA to Create a Database

3-27 Copyright © 2004, Oracle. All rights reserved. Summary In this lesson, you should have learned to: Compare SQL Server and Oracle database concepts Explore the Oracle Database 10g architecture Use the Database Configuration Assistant to create an Oracle database

3-28 Copyright © 2004, Oracle. All rights reserved. Practice Overview: Creating an Additional Database This practice gives you experience in using the DBCA to create an additional database called MTG. Note: Completing this practice is critical for several of the following practice sessions.