1 Database Architectures Modified from …..Modern Database Management Jeffrey A. Hoffer, Mary B. Prescott, Fred R. McFadden

2 Web Systems – client/server interactions Networked computing model Networked computing model Processes distributed between clients and servers Processes distributed between clients and servers Client – A machine (PC or could be another server) that requests and uses a service Client – A machine (PC or could be another server) that requests and uses a service Server – Machine (PC/mini/mainframe) that provides a service Server – Machine (PC/mini/mainframe) that provides a service For DBMS, server is a database server For DBMS, server is a database server

3 Application Logic in Client/Server Systems Presentation Layer Presentation Layer Input – keyboard/mouseInput – keyboard/mouse Output – monitor/printerOutput – monitor/printer Business Layer Business Layer I/O processingI/O processing Business rulesBusiness rules Data managementData management Data Layer Data Layer Data storage/retrievalData storage/retrieval GUI Interface Procedures, functions, programs DBMS activities

4 Client/Server Architectures File Server Architecture File Server Architecture Database Server Architecture Database Server Architecture Client does extensive processing Client does little processing

5 File Server Architecture All processing is done at the PC that requested the data All processing is done at the PC that requested the data Entire files are transferred from the server to the client for processing. Entire files are transferred from the server to the client for processing. Problems: Problems: Huge amount of data transfer on the networkHuge amount of data transfer on the network Each client must contain full DBMSEach client must contain full DBMS Heavy resource demand on clients Heavy resource demand on clients Client DBMSs must recognize shared locks, integrity checks, etc. Client DBMSs must recognize shared locks, integrity checks, etc. FAT CLIENT

6 Figure 9-2 – File Server Architecture FAT CLIENT

7 Database Server Architectures Client is responsible for Client is responsible for I/O processing logicI/O processing logic Some business rules logicSome business rules logic Server performs all data storage and access processing  DBMS is only on server Server performs all data storage and access processing  DBMS is only on server Advantages Advantages Clients do not have to be as powerfulClients do not have to be as powerful Greatly reduces data traffic on the networkGreatly reduces data traffic on the network Improved data integrity since it is all processed centrallyImproved data integrity since it is all processed centrally Stored procedures  some business rules done on serverStored procedures  some business rules done on server

8 2-tier Database server architecture Thinner clients DBMS only on server

9 2-Tier Architecture OR

10 Three-Tier Architectures Three layers: Three layers: ClientClient Application serverApplication server Database serverDatabase server Thin Client PC just for user interface and a little application processing. Limited or no data storage (sometimes no hard drive) GUI interface (I/O processing) Browser Business rules Web Server Data storage DBMS

11 3-tier architecture Thinnest clients Business rules on separate server DBMS only on DB server

12 3-Tier (n-tier) Architecture OR

13 Advantages of Three-Tier Architectures Scalability Scalability Technological flexibility Technological flexibility Long-term cost reduction Long-term cost reduction Better match of systems to business needs Better match of systems to business needs Improved customer service Improved customer service Competitive advantage Competitive advantage Reduced risk Reduced risk

14 Challenges of Three-tier Architectures High short-term costs High short-term costs Tools and training Tools and training Experience Experience Incompatible standards Incompatible standards Lack of compatible end- user tools Lack of compatible end- user tools

15 Application Partitioning Placing portions of the application code in different locations (client vs. server) AFTER it is written Placing portions of the application code in different locations (client vs. server) AFTER it is written Advantages Advantages Improve performanceImprove performance Improve interoperabilityImprove interoperability Balanced workloadsBalanced workloads

16 Processing Logic Distributions 2-tier distributions n-tier distributions Processing logic could be at client, server, or both Processing logic will be at application server or Web server

17 Parallel Computer Architectures Tightly Coupled Tightly Coupled Symmetric Multiprocessing (SMP)Symmetric Multiprocessing (SMP) Multiple CPUsMultiple CPUs Shared RAMShared RAM Loosely Coupled Loosely Coupled Massively Parallel Processing (MPP)Massively Parallel Processing (MPP) Multiple CPUsMultiple CPUs Each CPU has its own RAM spaceEach CPU has its own RAM space

18 Parallel Computer Architectures Figure 9-6 – Tightly-coupled – CPUs share common memory space Figure 9-7 – Loosely-coupled – CPUs each have their own memory space

19 Query Processing with Parallel Processors Figure 9-5(a) – Parallel transactions Figure 9-5(b) – Parallel query

20 Don’t forget Grid computing The creation of a "virtual supercomputer" by using a network of geographically dispersed computers. The creation of a "virtual supercomputer" by using a network of geographically dispersed computers.

21 Middleware Software which allows an application to interoperate with other software Software which allows an application to interoperate with other software No need for programmer/user to understand internal processing No need for programmer/user to understand internal processing Accomplished via Application Program Interface (API) Accomplished via Application Program Interface (API) “glue” The “glue” that holds client/server applications together

22 Types of Middleware RPC – Remote Procedure Calls (RPC) RPC – Remote Procedure Calls (RPC) client makes calls to procedures running on remote computersclient makes calls to procedures running on remote computers synchronous and asynchronoussynchronous and asynchronous Message-Oriented Middleware (MOM) Message-Oriented Middleware (MOM) asynchronous calls between the client via message queuesasynchronous calls between the client via message queues Publish/Subscribe Publish/Subscribe push technology  server sends information to client when availablepush technology  server sends information to client when available Object Request Broker (ORB) Object Request Broker (ORB) Object-oriented management of communications between clients and serversObject-oriented management of communications between clients and servers SQL-oriented Data Access SQL-oriented Data Access Middleware between applications and database serversMiddleware between applications and database servers

23 Client/Server Security Network environment  complex security issues Network environment  complex security issues Security levels: Security levels: System-level password securitySystem-level password security for allowing access to the system for allowing access to the system Database-level password securityDatabase-level password security for determining access privileges to tables; read/update/insert/delete privileges for determining access privileges to tables; read/update/insert/delete privileges Secure client/server communicationSecure client/server communication via encryption via encryption