MS-SQL SERVER ARCHITECTURE

MS-SQL SERVER ARCHITECTURE

1. DBA
Architecture
Intro

2. Introduction
MS SQL Server is a database server
Product of Microsoft
Enables user to write queries and other SQL
statements and execute them
Consists of several features. A few are:
◦Query Analyzer
◦Profiler
◦Service Manager
◦Bulk Copy Program (BCP)

3. Profiler
Monitoring tool
Used for performance tuning
Uses traces –an event monitoring protocol
Event may be a query or a transaction like logins etc

4. Service Manager
Helps us to manage services
More than one instance of SQL server can be
installed in a machine
First Instance is called as default instance
Rest of the instances (16 max) are called as named
instances
Service manager helps in starting or stopping the
instances individually

5. Instances
Each instance is hidden from another instance
Enhances security
Every instance has its own set of Users, Admins,
Databases, Collations
Advantage of having multiple instance is
◦Multi company support (Each company can have its
own instance and create databases on the same server,
independent on each other)
◦Server consolidation (Can host up to 10 server
applications on a single machine)

6. BCP
Bulk Copy Program
A powerful command line utility that enables
us to transfer large number of records from a
file to database
Time taken for copying to and from database
is very less
Helps in back up and restoration

7. Query Analyzer
Allows us to write queries and SQL statements
Checks syntax of the SQL statement written
Executes the statements
Store and reload statements
Save the results in file
View reports (either as grid or as a text)

8. SQL Database Objects
A SQL Server database has lot of objects
like
◦Tables
◦Views
◦Stored Procedures
◦Functions
◦Rules
◦Defaults
◦Cursors
◦Triggers

9. System Databases
By default SQL server has 4 databases
◦Master : System defined stored procedures, login details,
configuration settings etc
◦Model : Template for creating a database
◦Tempdb: Stores temporary tables. This dbis created when
the server starts and dropped when the server shuts down
◦Msdb: Has tables that have details with respect to alerts,
jobs. Deals with SQL Server Agent Service

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

11. 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
Oracle SQL Server
Table Table
Index Index
View View
Synonym Synonym
Sequence Identity Columns
Procedure Stored Procedure
Function Function
Package N/A
Queue in Streams Advanced Queuing Service Broker Queue
Object Type Type
XML DB XML Schema Collection
Comparison of Core Schema and Data Structures (Objects)

12. 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
Data FileData FileData File Data FileData FileData File
Temporary TablespaceGroups
Tablespace
ExtentExtent
FilegroupTablespace
Segment Segment
ExtentExtent
Filegroup
Heap/Index Heap/Index
ExtentExtent Extent
BlocksBlocksBlocks Blocks Pages Pages Pages

13. 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 Variable 64 KB fixed
Segment
Any logical structure
that is allocated
storage
No equivalent structure

14. Storage
Allocation
Fundamental difference in storage allocation between Oracle
and SQL Server2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
2K
block
6 x 2K = 12K
EXTENT
8 x 2K = 16K
EXTENT
12K + 16K = 28K
SEGMENT
(Table/Index)
8K
block
8K
block
8K
block
2K
block
8K
block
8K
block
8K
block
2K
block
8K
block
8K
block
8K
block
2K
block
8K
block
8K
block
8K
block
2K
block
8K
block
8K
block
8K
block
2K
block
8K
block
8K
block
8K
block
2K
block
8K
block
8K
block
8K
block
2K
block
8K
block
8K
block
8K
block
2K
block
8 x 8K = 64K
EXTENT
8 x 8K = 64K
EXTENT
64K + 64K =
128K
HEAP/INDEX
Oracle SQL Server

15. 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

16. Managing Extents and Pages
(Continued)
Current Use of Extent
GAM Bit
Setting
SGAM Bit
Setting
Free, not being used 1 0
Uniform extent, or full
mixed extent
0 0
Mixed extent with free
pages
0 1
File Header Extent
Extents in
SQL Server
GAMs and SGAMs

17. Tablespacesand 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/filegroupsare used to group application objects
Tablespaces/filegroupsoptimize administration of data files

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

19. Mapping of Tablespaces
and Filegroups
System Tablespace
SysAuxTablespace
Temporary
Tablespace
BigFileTablespace
User Data Tablespace
User Index
Tablespace
Undo Tablespace
Redo Log Files
Master DB
Resource DB
TempDB
Model DB
MSDB
User DB
Data FG
Index FG
Log File(s)
Oracle Database InstanceSQL Server Instance
Data file
Data fileData file
Data fileData file
TablespaceGroup
Data fileData file
Data fileData file
Data fileData file
Data fileData file
Data fileData file
Redo Log
Redo Log
Redo Log
Log fileData file
Log fileData file
Log fileData file
Log fileData file
User Database
Data fileData file
Data fileData file
Log file
Log fileData file

20. 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.

21. 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