1. Module 2: Database Architecture

2. Overview Schema and Data Structure (Objects) Storage Architecture
Data Blocks, Extents, and Segments
Storage Allocation
Managing Extents and Pages
Tablespaces and Datafiles
SQL Server Data Files
Mapping of Tablespaces and Filegroups
Logging Model
Data Dictionary

3. Schema and Data Structures (Objects)
Schema – a collection of objects owned by a database user
Schemas in SQL Server provide logical separation of objects, similar to Oracle’s schema
Comparison of Core Schema and Data Structures (Objects)
Oracle
SQL Server
Table
Index
View
Synonym
Sequence
Identity Columns
Procedure
Stored Procedure
Function
Package
N/A
Queue in Streams Advanced Queuing
Service Broker Queue
Object Type
Type
XML DB
XML Schema Collection

4. Temporary Tablespace Groups
Storage Architecture
Database storage architecture includes physical and logical structures
Physical structures are data files, log files, and operating system blocks
Logical structures are subdivisions of data files used to manage storage space
Physical
Data File
Data File
Data File
Data File
Data File
Data File
Temporary Tablespace Groups
Tablespace
Tablespace
Filegroup
Filegroup
Logical
Segment
Segment
Heap/Index
Heap/Index
Extent
Extent
Extent
Extent
Extent
Extent
Extent
Blocks
Blocks
Blocks
Blocks
Pages
Pages
Pages
ORACLE
Sql sERVER

5. Data Blocks, Extents, and Segments
Structure
Oracle
SQL Server 2008
Smallest unit of logical storage
Block
Page
Block size
Variable
8 KB fixed
Storage allocation
Performed in multiple blocks; are ‘extents’
Performed in multiple pages; are ‘extents’
Extent size
64 KB fixed
Segment
Any logical structure that is allocated storage
No equivalent structure

6. Storage Allocation
Fundamental difference in storage allocation between Oracle and SQL Server

7. Managing Extents and Pages
In Oracle, each extent is dedicated to an allocated object. In SQL Server, the equivalent is a uniform extent.
SQL Server uses mixed extents: pages are allocated to objects with less than 8 blocks of data
Similar to the Oracle bitmap functionality used to manage free space and extent allocation, SQL Server uses the Global Allocation Map (GAM) and Shared Global Allocation Map (SGAM)
Oracle keeps track of extents using extent allocation maps

8. Managing Extents and Pages (Continued)
File Header Extent
Extents in SQL Server
Current Use of Extent
GAM Bit Setting
SGAM Bit Setting
Free, not being used 1
Uniform extent, or full mixed extent
Mixed extent with free pages
GAMs and SGAMs

9. Tablespaces and Data files
Oracle and SQL Server store data in data files
The largest logical storage structure in Oracle is a tablespace
The largest logical storage structure in SQL Server is a filegroup
Tablespaces/filegroups are used to group application objects
Tablespaces/filegroups optimize administration of data files

10. SQL Server Data Files Three file types supported by SQL Server:
Primary Data Files
Secondary Data Files
Log Data Files

11. Mapping of Tablespaces and Filegroups
System Tablespace
SysAux Tablespace
Temporary Tablespace
BigFile Tablespace
User Data Tablespace
User Index Tablespace
Undo Tablespace
Redo Log Files
Data file
Log file
Data file
Master DB
Resource DB
TempDB
Model DB
MSDB
User DB
Data FG
Index FG
Log File(s)
Data file
Log file
Data file
Tablespace Group
Log file
Data file
Data file
Log file
Data file
Data file
Log file
Data file
Data file
Data file
User Database
Data file
Data file
Data file
Data file
Redo Log
Log file
Oracle Database Instance
SQL Server Instance

12. Demonstration 1: Viewing an Instance’s System Databases
In this demonstration you will see how to:
Connect to an instance
Review system databases
Review application or user databases

13. Logging Model
Oracle uses online redo logs to record changes made to the database by transactions and undo segments to capture the ‘before image’ of data
SQL Server implements both of these functions using transaction logs. Each transaction record contains the undo and redo image of the transaction.

14. Data Dictionary
In Oracle the data dictionary is stored under the SYS schema in the SYSTEM tablespace
In SQL Server the data dictionary consists of:
Catalog View—the best way to access system metadata
Backward Compatibility Views—All system tables from previous releases are provided as backward compatibility views
Dynamic Management Views—to view the current state of the SQL Server system. Provide real-time snapshots of internal memory structures indicating the server state.
INFORMATION_SCHEMA views—SQL-99 method to view system metadata
SQL Server’s Resource database contains the metadata for system stored procedures

15. Demonstration 2: View the Data Dictionary
In this demonstration you will learn how to:
View the dictionary with object explorer
View the data dictionary with catalog views
View the data dictionary within a database
View the data dictionary via system stored procedures

16. Review Defined schema and identified core schema objects
Examined the storage architecture and its physical (datafiles, logfiles, and so on) and logical structures (blocks, extents, segments, and tablespaces)
Defined the hierarchy in the logical structures
Compared Oracle and SQL Server in terms of schema vs. databases, and tablespaces vs. filegroups
Examined the structures used in the implementation of the logging model (redo logs and rollback segments in Oracle vs. transaction logs in SQL Server)
Brief look at the location and composition of the data dictionary/system catalog