SYBASE

SQL Server Backgrounder

SQL Server provides a unique and flexible database serversolution for multi-user PC applications, from simple decisionsupport to large on-line, transaction processing systems. SQLServer is based on Sybase, Inc.'s field-proven relational databasemanagement system, enhanced with technology from Microsoft anddatabase technology from Ashton-Tate. The result is a productuniquely positioned to address the needs of the evolving PC databasemarket.

Market Evolution

Today's PC hardware is capable of running applicationspreviously limited to mini or mainframe systems. OS/2, the new PCoperating system developed by Microsoft and IBM, provides multi-tasking support previously found only in the mini-mainframe world.Within a year, new systems running OS/2 with several megabYtes of.memory and disk drives in the hundreds of megabytes will becommonplace in PC networks.

PC databases provide tremendous productivity benefits includingindividual control, quick access, and the ability to quickly developcustom applications. However, most existing PC database softwarewas developed for a generation of PC's that had limited memory, anda single user, single tasking operating system. Today's PCdatabases have generally operated separate from large corporateproduction-oriented information systems. In large corporationstoday's PC databases are used as decision support systems. Incontrast, mini and mainframe relational database products, althoughpowerful, for the most part lack a sophisticated user interface, andstill use the older character-oriented terminal technology. Whilethe mini-mainframe SQ~-based relational databases have the power tosupport on-line production applications, they traditionally lackmulti-user performance, the ability to enforce complex dataintegrity rules, and high database availability.

Client/Server lIed.l

In response to these trends, both PC and mini/mainframedatabases are adoptin~ the "client/server" model of computing(sometimes also called the workstation/server model). Thisapproach splits the functions of a database management systemcleanly into a "front-end" component where data is manipulated byend users or applications, and a "back-end", or server componentwhere data is stored and retrieved. In PC networks, front-endstypically run on wor~ation PC's and back-ends on server PC's.

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Ashton-Tatt: Corporation

Microsoft Corporation

Sybase. Inc.

20101 Hamilron Avenue. Torrance, California 90502-1319

16011 NE 36th WilY, Box 97017. Redmond. Washin!:ton 98073-9717

2910 Sevenrh Street, Berkeley, California 94710

SQL Server Backgrounder 2-2-2

A major advantage of the client/server model is that manyclients can communicate over a network to single or multipleservers. This approach requires that the server be an intelligentdatabase that has the ability to evaluate the client's request andreject unauthorized database actions. Unlike conventional databasesoftware that requires data integrity and transaction logic to becoded into each application, the intelligent server allows dataintegrity and transaction logic to be stored centrally in thedatabase itself. This effectively brings mainframe level control tothe PC environment. Rules governing an organization can be enforcedcentrally in a PC local area network, just as they would have beenon a mainframe. From a programming and maintenance perspective,this translates into important user benefits. Once rules areestablished in the central database, changes can be made quickly andeasily, while maintaining a high level of integrity and performance.

Separating workstations and servers also permits the server toact as a dedicated database machine that can be tuned to aparticular application or set of applications and scaled in size.The server must be able to support not only increasing amounts ofdata, but also increasing numbers of workstations withoutsignificantly degrading response time. As application databaserequirements grow, a server that started out on a PC should be ableto move to a larger PC or to a mini/mainframe if necessary, withoutrequiring changes to the user interface. .

SQL Server

SQL Server meets the requirements of the client/server model byproviding an intelligent server that runs in a local area network.

SQL Server is an open platform, offering any workstationapplication the ability to access high-performance, back-enddatabase services. This gives users the ability to use a variety ofPC applications and languages, against the same data at the sametime for any DOS or OS/2 workstation in a local area network.

On the server side, SQL Server's distributed databasecapabilities extend this flexibility even further, allowing multipleworkstations to talk with multiple servers.

SQL Server is based on the ANSI standard Structured QueryLanguage (SQL), the industry-standard language by which applicationscommunicate with databases. SQL gives programmers common toolsacross many different systems and ensures that applicationinvestments are preserved as systems grow and change over time. SQLcan also serve as the common communications vehicle acrossrelational databases on different systems. SQL Server is completely

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SQL Server Backgrounder 3-3-3

compatible with the SYBASE DataServer running on larger platformssuch as the DEC VAX. For all of SQL's importance, many end-usersmay never want to use SQL directly. One of SQL Server's keybenefits is that end-users can use their front-end application ofchoice, and still enjoy the power and flexibility of a SQL-basedback-end.

dBASE Support

SQL Server in combination with a future version ofAshton-Tate's dBASE will provide transparent mapping of dBASE toSQL. This mapping is made possible through both the use of many ofSQL Server features and through technology provided by Ashton-Tatethat will be incorporated into SQL Server. Applications written inthe dBASE language will be able to use the SQL server with nomodification.

Through this transparency a mechanism is provided to the largeinstalled base of dBASE customers to migrate to the Client-Serverarchitecture.

SQL Server Architecture

SQL Server is a true database server, providing high- ,performance database services, integrity logic, data dictionary andadministration facilities. In contrast to a file server, whichrelies on operating system file handling facilities, SQL Server'talks directly to OS/2 at the physical disk level. Further, mostSQL databases coming from the mini and mainframe world have anarchitecture that requires a process per user. While such anarchitecture may work on large systems, it is not suitable forPC's. SQL Server is designed so that a single process runs thewhole database. A SQL kernel runs under OS/2, scheduling tasks fromdifferent users and the disk simultaneously, thereby making veryefficient use of memory. Once SQL Server is loaded, a PC servermachine can support more than 25 users in each additional megabyteof memory.

SQL Server's lower memory requirements leave more memoryavailable for the disk cache, which in turn reduces disk I/O's andmaximizes use of the CPU. This maximizes transaction throughout, sothat SQL Server's performance, as seen by an individual user, staysvirtually constant as users are added to the network.

SQL Server's architecture is further tailored to the on-lineenvironment by providing high availability features such as on-linebackup and recovery. Database updates, design changes, performancetuning, and integrity rule changes can all be done while thedatabase is still running. The system can be administered fromanywhere on the network, so there is no need for a separateadministrator's console.

SQL Server Backgrounder 4-4-4

The client workstation communicates with SQL Server over PCnetworks using TRANSACT-SQL, a superset of ANSI standard SQL with aset of powerful Sybase-developed extensions. These extensionsinclude control of flow, temporary--variables,transactionmanagement, and stored procedures, the latter being pre-compiled SQLqueries.

Stored procedures dramatically minimize message and networktraffic from the workstation to the server, and can result inperformance that is 10 times greater than standard SQL queries.Stored procedures also allow SQL Server to centrally enforce dataintegrity, a far superior approach to requiring integrity rules inall the various front-end applications which access the database.

The SQL Server client is an OS/2 or DOS based workstation thatconsists of several pieces: OS/2 or DOS; networking software;DB-LIBRARY, the standard application interface to SQL Server; andthe workstation application itself.

A five megabYte 386-based SQL Server can be expected to supportmore than 35 users accessing a 300 megabYte database with subsecondresponse time. Should the need arise, it is also possible to moveSQL Server applications to mini computers and mainframe databasesthat are based on SQL. .

SQL Server and Workgroup Computing

SQL Server has been designed to become the database cornerstonefor PC workgroup computing.

For DOS and OS/2 based workstation applications, of whichdBASE is the leading PC database example, SQL Server will be thepowerful multi-user option that preser.Yescurrent applicationsinvestments while broadening the accessibility and performance ofthose same applications.

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dBASE and Ashton-Tate are registered trademarks of Ashton-TateCorporation.Microsoft is a registered trademark of Microsoft Corporation.SYBASE is a registered trademark and DataServer, TRANSACT-SQL, andDB-LIBRARY are trademarks of Sybase, Inc.