Database Architecture


A database is similar to a data file that stores application data. Like the data file, a database doesn t present information directly to the user. The end user runs an application that is responsible for accessing the data and presenting it to the end user in an understandable format. The main difference between a data file and a database is that a database is a highly organized data structure. In a well-defined database, there is no storage of duplicate data. All related pieces of information are joined together to form objects. These objects, defined in records, represent a specific type of data relationship or data structure.

When working with data files, developers are required to write code that defines specific structures represented within a data file. The database contains a catalog of applications that determine how data is organized. Based on the credentials and connection information offered by the user, the catalog is responsible for dynamically presenting the requested data. Databases are organized into a holding file, which contains an optimized storage structure for data, and the Database Management System (DBMS), responsible for enforcing and maintaining the database schema.

The DBMS maintains the data relationships between the database elements and ensures that the data is stored according to a defined structure. Also, the DBMS provides recovery points in case of system failures. SQL Server 2000 uses a transaction log of each database transaction. This transaction log is a serial record of all modifications that have occurred in the database as well as the transactions for each of the modifications. This log records the start of each transaction and any changes made, as well as maintains enough information to undo the modification if necessary.

Application architecture defined by the SOA has implemented a shift in how databases are used to present and store data. Traditionally, databases were segmented into a separate application tier and provided only data storage. SOA has promoted them to first-class service providers and a strategic repository for business logic.

Which Is the Right Database?

Both SQL Server and Microsoft Access are relational databases used within many enterprises and application solutions. Each one is designed to solve a specific business need, and it is important to understand where they differ in feature and functionality. SQL Server is a true relational database management and analysis system designed to deliver a highly scalable line of business solutions, analysis, and data warehousing solutions. Microsoft Access is a relational database system designed for less scalable solutions and ideal for many offline scenarios. Designed with different architectures, the two databases can interoperate and this offers a hybrid solution that solves additional application integration issues. Table 5.1 shows some important differences between the two architectures that are important to keep in mind when you re designing a database application.

Table 5.1: Major differences between Microsoft Access 2003 and SQL Server 2000.

Design Factor

Microsoft Access 2003

SQL Server 2000

Data Integrity

Provides no data logging and offers no recovery point to restore from. Is designed for smaller applications that are not considered mission mission critical.

Logs all transactions and provides point-in-time recovery. Is an ideal solution for critical data.

Concurrency

Depends on the implementation; offers simultaneous access for reading data; a practical limit is less than a hundred and that depends heavily on the available memory and disk space. This number also decreases depending on the amount of database querying.

Is an enterprise-wide database that supports a variety of configurations that allow an almost unlimited number of users to access the database.

The design of SQL Server is optimized for memory and disk space.

Management Features

Is easy for end users to administer and manage as the tools are built into the database. All management is done on a single database only.

Is more complex to administer but provides a rich set of tools that allow administration of both the database and data across the entire database catalog.

Database Size

As database size increases , the performance will decrease.

Database size isn t a factor in performance.

Design considerations are import as well as the actual physical limitations. Table 5.2 outlines the basic physical limitations of both databases.

Table 5.2: Physical limitations of Microsoft Access 2003 and SQL Server 2000.

Feature

Microsoft Access 2003

Microsoft SQL Server 2000

Database Size

2 gigabytes minus the space needed for system objects

Terabytes

Number of Database Objects

32,768

2,147,483,647

Security

Based on user or workgroup information file

Integrated with Windows 2000 and NT security

Analysis Services (Data Mining, OLAP, Data Warehousing)

None

Built in

SMP Support

None

Built in

Clustering

None

Built in




Programming Microsoft Infopath. A Developers Guide
Programming Microsoft Infopath: A Developers Guide
ISBN: 1584504536
EAN: 2147483647
Year: 2006
Pages: 111
Authors: Thom Robbins

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