Chapter 1 Sybase System 11 Strategy

Overview

System 11 is a set of components that provides enterprise solutions for a wide range of database applications including data warehousing, on-line transaction processing (OLTP), decision support systems (DSS), and mass deployment. It works equally well over a variety of platforms from laptops to high-end clustered multiprocessing systems. The Sybase client/server family of products gives database system developers the flexibility to create solutions for an enormous range of distributed computing applications and to integrate almost any variety of hardware platforms and operating systems.

This chapter is an overview of the Sybase approach to distributed computing solutions and provides the technological context within which SQL Server fits. The discussion is based on the following topics:

Sybase Meets Today's Market Requirements

Sybase recognizes that the models governing enterprise computing are changing rapidly. Decentralization, transition, and increasing demands for efficiency are now the norm. Rather than try to elude these new paradigms, companies must incorporate them in a productive way to achieve success and stay ahead of the competition. These paradigms effect business in the following ways:

Decentralization The workforce is becoming increasingly decentralized as higher numbers of employees telecommute, more field employees use mobile computing to maintain links to their offices, and organizations do more of their business on a global scale.
Transition Transition in every aspect of the workplace is now the norm as work models and tools continually evolve and change.
Efficiency In a perpetual effort to beat the competition, organizations try to do more with less. Improving efficiency has become a way of doing business¯not just an interim adjustment.

Organizations need the infrastructure that can help them to be the pace setters¯or they fall hopelessly behind. They need tools that ease the difficulty of constant change and the burden placed on employees as a result of streamlining measures.

A Family of High-Performance Products

Sybase recognizes the need for an infrastructure that can support the enterprise. For the next several years we'll be living in a multi-paradigm world: mainframes, client/server, and the Internet. Organizations will need to extend their legacy systems and develop applications for client/server and the Internet.

Sybase has developed a clear vision about technology needs now and for the future. This vision has produced a highly flexible product offering with customizable options for the three major classes of distributed applications: OLTP, data warehousing, and mass deployment. Organizations implement these applications using the three technology layers¯database, middleware, and tools¯as follows:

At the database layer, Sybase offers a family of servers to implement fast, scalable data warehouses, OLTP, and mass deployment applications.
At the middleware layer, Sybase provides server and interoperability products for data replication, enterprise messaging, and interoperability in any heterogeneous computing environment.
At the tools layer, Sybase helps you develop and manage your system with administration and monitoring products, tuning, application development and debugging tools, and hundreds of Sybase Open Solutions Partner third-party applications.

Figure 1-1 summarizes Sybase's product strategy. It represents adaptive and complete system solutions. The architecture is adaptive because you can customize the components to meet your organization's distributed computing needs at every layer. The architecture is complete because Sybase products are fully integrated and optimized to work together. Also, because the products in each cell of the matrix are independent, you can use Sybase products with third-party products. For example, you can use a Sybase database with third-party middleware and tools, or you can use Sybase middleware and tools with third-party database engines.

Mainframe Computing

Mainframe computing was the popular computing model before the client/server model became the widespread standard. In mainframe computing, the mainframe performs all processing and uses a "dumb" terminal (one with no processing power of its own) as a display unit. For example, retrieving and displaying employee information on a terminal requires the following steps:

: 1. Display a form on the terminal into which a user can enter an employee ID.
: 2. Accept the employee ID information.
: 3. Validate the format of the information.
: 4. Check the availability of the employee information.
: 5. Get the employee information from the database.
: 6. Format the data for display on the users terminal.
: 7. Display the employee information on the terminal.

We can categorize these tasks as those related to data presentation (steps 1, 6, and 7), those related to data validation (steps 2 and 3), and those related to data access (steps 4 and 5). The mainframe performs all of the steps because the terminal has no processing capability.

In the mainframe processing model, the server is heavily loaded because it performs all of the processing for every client. In the client/server model, however, clients can perform some portion of the application processing, such as data presentation and some data validation. This off-loading of some tasks to clients with processing power improves performance because the server has more time for processing requests.

Client/Server Computing in the Database Environment

In just the last few years, the client/server model has gone from being the "new trend" in distributed (networked) computing to the "traditional model" for implementing distributed computing. It divides processing into client applications and server applications that cooperate to accomplish tasks for the integrated application.

An Overview of Client/Server Concepts

Client applications make requests for service. Server applications receive requests and respond by returning data or other information to client applications, or by taking some action.

Figure 1-2 depicts a common client/server interaction. In this example, the client application makes a request and delivers it to the server. The server application receives the request and processes it. The server then takes action and/or returns a result to the client. The client receives the result (if a result was returned) and uses it to continue the task it was performing.

Figure 1-2: Basic client/server interaction

Sometimes a server can itself become a client to another server. Say Client A makes the request "print file chapter.doc". Server A retrieves chapter.doc from the file system and becomes a client to the printer server. Server A remains a client until the print job is done. If the printer server could not print chapter.doc, then Server A might return an error message to Client A to let it know that its request could not be granted.

Benefits of Client/Server Computing

Here are a few of the many advantages that client/server computing offers over the computing models that came before it:

Simplifies computer interactions for the user because smart clients implemented on desktop workstations present graphical user interfaces (GUIs) and multimedia applications. The cost of developing applications that use these types of interfaces for desktop workstations is less expensive than it is for the servers in mainframe computing.
Reduces network traffic, which improves performance. Consider the example given previously in the section ``Mainframe Computing''. The mainframe model requires three network events: in step 1 when the host must display the form on the screen; in step 2 when the client sends the employee ID back to the host; and in step 6 when the host sends the employee information back to the terminal and displays it. The same example using the client/server model requires only two network events: for step 4 when the client sends the employee ID to the server and in step 6 when the server sends the employee information back to the client.
Allows an organization to use a variety of equipment to meet the needs of different applications and users because it supports a heterogeneous environment. Programmers can get the processing power they need from workstations, and managers can work with computers that are best for creating schedules and other spreadsheets using desktop computers. The organization can save money by giving each employee the right amount of computing power needed to do their jobs.
Facilitates implementation of open systems because it is built around the International Standards Organization (ISO) Reference Model for networked systems. This model specifies an application programming interface (API) layer which hides the intricacies of lower level software, making it easy to add new hardware and applications.

Client/Server Nodes and Implementation

Client and server applications can reside on the same computer, or node; however, in a distributed computing environment, they usually reside on different nodes. Nodes are distinguished as client nodes and server nodes depending on their role.

Client nodes tend to be generalized. Computers that run client applications may include many types of clients, such as a directory client, a file client, and a print client. There are often many nodes running the same client applications so that a single server node, such as a print server, serves several client nodes. Although a single server node can accommodate more than one server application, system designers often implement server applications on dedicated server nodes because servers tend to be more specialized and require more processing and system resources than clients.

A server application is typically a continuous process (for example, a daemon in UNIX) while a client application is most often a standard application program. During the course of its normal processing, a client application calls API routines to send the requests to a server. When the client has finished its work, it stops execution. As a dedicated process, the server runs continuously: it waits for requests, detects them, processes them, returns the results, and then waits for the next request.

Figure 1-3 shows a typical relationship between client and server nodes on a network. Each client accesses all servers: database server, file server, and print server. The print server might be a client to the file server and the file server could be a client to the database server.

Figure 1-3: Client and server nodes on a network

Relative Roles of Clients and Servers

The terms "client" and "server" characterize relative roles rather than absolute roles. For example, in executing a print request, the print server becomes a client if it has to ask a file server to send it a copy of the file it is going to print.

Architecture is fully functional when it allows clients to act as servers and servers to act as clients when necessary. For example, Sybase implements this capability with the Open Client and Open Server products. Sybase applications that have both client and server functionality incorporate both Open Client and Open Server libraries.

Figure 1-4 shows an example in which an application acts as both a client and a server. As a server, it responds to requests from and returns results to the Open Client application. As a client, it makes requests of the SQL Server and processes the results of those requests.

Figure 1-4: An application can act as both client and server

Sybase Client/Server Database Environment

In the Sybase client/server database environment, SQL Server runs all of the actual database management system¯it does all the processing associated with database access. The database server carries out the tasks initiated by client requests directed to the database. It is built on a multithreaded architecture and ensures data integrity, concurrency control, and the ability to recover from failures. The database server also maintains the data dictionary which defines the structure and contents of the database. The database client performs all the processing not associated with database access.

In the Sybase environment, "the database server" is SQL Server and "the database client" is any client software that can interact with SQL Server. The Sybase interactive SQL utility, ISQL, for example, is a client application that you use with SQL Server to execute ad hoc SQL queries. Files can be used as both the input source and the output destination. In general, the database client contains application-specific functionality and the processing related to interactions with the user's terminal such as typing characters to the screen, displaying cursor motions, and mapping the keystrokes.

It is more common for users to work with a program's GUI than for them to interact directly with the program. These GUIs are often forms into which the user enters information. For example, when a patient checks into a hospital, the intake nurse types registration information into a form managed by the client application. The client might perform input checking to make sure that the data entered is consistent with the type of information it should be. For example, it might check that the date entered for "Date of Birth" is a real date. The client then takes the information the user typed in and uses it retrieve or modify data via the server.

Configurations that Leverage Your Investment

Now that we've described what we mean by "client/server" computing, we can revisit the matrix shown in Figure 1-1. The Sybase product family provides a wide range of options and configurations with which to create any number of solutions for enterprises with distributed database requirements. The most common client/server configurations are based on the two-tier and three-tier models. The tiers use solutions from the database, middleware, and tools layers shown in Figure 1-1.