18th Chapter-delphi Client Server application development (i) (3)

18.1.3 various database server function introduction

Server data management includes several software that enables users to access any node in the network and to ensure confidentiality, recoverability, and integrity in a multiuser environment. As mentioned earlier, the basic access link in client/server computing is SQL, which is a high-level, non-process database language, and has now developed a number of back-end servers and DBMS that support SQL. These products are described below.

18.1.3.1 DB2

DB2 is an RDBMS developed by IBM. It uses SQL to perform all database operations. Data definition, data access, data manipulation, and authorization capabilities. SQL statements are entered or nested in an application by the user at a client node from the keyboard.

The DB2 structure includes tables, views, table spaces, indexes, index spaces, databases, and storage groups. This RDBMS provides tools that allow users to dynamically build and modify these structures. DB2 also includes parallel processing software to control and restrict intervention, fallback and recovery functions, and security assurances.

Parallel processing is done through locks, and when the application reads the database data, DB2 acquires a shared lock on the data, allowing other applications to read the same data. If an application needs to modify the data, then DB2 puts a mutex lock on the data to prevent other applications from accessing the data. DB2 also provides some options for the level of the lock or the size of the lock.

DB2 periodically stores and checks all database changes. All changes residing in the system buffer are written to the database, and a changed record is loaded into the log. All of the images that were established with the most recent changes to the log can be used to complete the recovery of system failures. DB2 includes utilities to re-establish the database from backup copies. This utility contains a selection that allows users to copy only those pages in the table space that have been modified since the last backup.

DB2 also contains some security requirements to protect the database.

18.1.3.2 Borland Object Component Architecture (BOCA)

Boca establishes a client/server architecture that considers both development tools and database management tools. It centralizes the level of object-oriented tools, middleware, and database server technologies together to provide a client/server solution. Components of the architecture are:

1. Advanced object-oriented Tools

Borland establishes a broad-based and tightly integrated object-oriented tool that leverages the benefits of current customer/server changes. Using object-oriented methodology, the following products were established: Borland C + +, Borland Delphi, Paradox, QuattroPro, Visual dbase, and Objectvision.

2. Idapi

The IDAPI (Integrated database application design interface) is a Borland SQL connectivity solution for the company. IDAPI enables developers to build database applications with greater efficiency, allowing users to access data stored in multiple database formats in a variety of hardware and operating system platforms as well as network environments.

3. InterBase

InterBase is a distributed SQL database server. It supports each database system querying the data and returning the information to any other InterBase server. The InterBase variable architecture represents the third wave of relational system technology, which enables InterBase to support efficient transaction processing and decision support transactions with minimal locks.

Borland's object-oriented technology enables developers to build complex client/server systems by structuring modular application components. These modular application components can be easily developed, tested, maintained, and enhanced and easily assembled into complex application packages, and Borland's visualization technology greatly improves software productivity.

18.1.3.3 Informix SQL Server series

Informix has launched a variety of products to meet specific customer/server requirements. They include Informix-on-line,informix Tp/xa,informix Star Informix on-line/optical and Informix on-line workstation editions.

Informix-on-line is an online transaction processing (OLTP) database server with the capabilities of availability, data integrity, and multimedia data management. It establishes an effective data storage method for fast data access, buffers data for minimal disk access, leverages multiprocessor features, allows simultaneous access by different processors, and automatically determines which is an effective search strategy, thus obtaining extremely high performance.

Informix-tp/xa connects on-line to the transaction management program, supporting transactions involving multiple databases and multiple DBMS (provided by different vendors). In many RDBMS, Informix first provides this standards-based interface to the transaction management program that is compliant with X/open XA.

Informix-star is a distributed client/server database product for on-line that delivers optimal performance and has minimal network traffic, site transparency, and high reliability of operating databases at different sites.

Informix-on-line/optical is an add-on product for on-line users. These users want to use optical devices with high-capacity storage capabilities on their database systems. On_line/optical allows a user to store blobs on a "write once read multiple" (WORM) optical subsystem. Users must have on-line/optical on-line and an optical subsystem. Of course, without this on-line/optical product users can still manipulate blobs on magnetic storage devices using on-line.

The Informix-on-line Workstation Edition is a graphical version of the on-line Administrator's manual. The workstation version has the same technical content as the hardware version, but it is structured in a windowed, point-and-click (point-and-click) graphics interface, using the keyword cross lookup. This allows the user to configure monitoring or tuning on-line in another window while accessing the required information in a window.

18.1.3.4 Microsoft SQL Server family

As part of the Microsoft SQL Server family, there are the following products: Microsoft SQL Server for Windows Nt,microsoft SQL Administrator for Windows,microsoft SQL Br Idge and Microsoft SQL Server Programmer Toolkit.

Microsoft SQL Server for Windows NT is designed to manage large databases and meet the needs of networked client/server applications for mission-critical application systems.

Microsoft SQL Bridge provides a protocol network between the Microsoft SQL Server environment and the Sybase SQL Server environment.

The Microsoft SQL Programmer Toolkit provides the flexibility to develop client/server applications that deliver critical portfolio information to windows-based, MS-DOS, and os/i build systems.