User's Guide Part I. Introduction to SQL Anywhere Chapter 3. Overview of SQL AnywhereSQL Anywhere Server products support connections from many users at a time, over a network. In this case, the database engine runs on one computer (the database server computer), while client applications run on other computers (client computers).
The SQL Anywhere server supports multiuser network access to SQL Anywhere. The SQL Anywhere standalone engine does not support multiuser access or network communications.
| PowerBuilder and InfoMaker users This chapter contains some information about connecting to a SQL Anywhere network server. The SQL Anywhere network server is not included with PowerBuilder and InfoMaker. |
The client side of the SQL Anywhere setup sends SQL queries and commands over the network to the server side, which carries out commands and sends the results of queries back to the client.
The SQL Anywhere Client is a program that handles network communications to the SQL Anywhere database server. The SQL Anywhere Client is a program named DBCLIENT (the Windows 3.x version is called DBCLIENW). The SQL Anywhere Client communicates with the SQL Anywhere network server. The standalone engine cannot handle communications from the SQL Anywhere Client.
For QNX, the database client is different from other operating systems. Instead of being a separate executable, the SQL Anywhere Client is a library named dbclient, which is loaded dynamically by client applications.
From the client application's point of view, there is no difference between the standalone setup and the network setup. In the single-user setup, a client application sends requests and commands to the database engine. In the multiuser setup, these requests are sent to the SQL Anywhere Client instead. In each case, the client application has a single point of contact with the DBMS. The additional complexity of handling requests in a multiuser, networked environment is hidden from the client application.
| Standalone applications work with the SQL Anywhere network server Once a client application is developed and working on a standalone SQL Anywhere setup on a single computer, no changes are needed to the application in order for it to work as a client application in a network environment against a SQL Anywhere server. |
For more information on the SQL Anywhere network server, see the SQL Anywhere Network Guide.
The SQL Anywhere standalone database engine is available for the Windows 3.x, Windows 95 and Windows NT, OS/2, and DOS operating systems. The SQL Anywhere database server is available for Novell NetWare, Windows 95 and Windows NT, OS/2, Windows 3.x, DOS, and QNX operating systems.
One SQL Anywhere database server can support multiple clients operating on different operating systems, communicating via different network protocols.
With a single database running on a single database engine, the default settings make the engine name, the database name, and the database file the same, apart from the path and extension associated with the file. In this situation there is little ambiguity when talking about the database .
In environments with multiple databases, multiple database files, and several database engines operating simultaneously, it is important to distinguish among the different components that make up a running SQL Anywhere DBMS.
| Term | Description |
|---|---|
| Database file | Even though the tables of a database may be held in several files on several disk drives, each database is identified by a single root file. Throughout this book, when reference is made to a database file, it is referring to the root file |
| Database name or alias | A SQL Anywhere database engine or server can run several databases simultaneously, managing access to each of them. When a database is started on a database engine, it is assigned a database name, also called the database alias. If no database name is explicitly assigned, the database receives the name of the root file with the path and extension removed |
| Server or engine name | When a database server or engine is started, it is assigned a server name or engine name. The server or engine name is entirely distinct from the name of the database engine program itself. By default, the server name is the first database name. For example, if a database engine is started with database C:\PB\EX\PSDEMODB.DB and no name is explicitly given, then the name of the engine is PSDEMODB |
| Clients and servers | Both the client side and the server side of a SQL Anywhere client/server setup consist of several components. The terms client and server themselves are commonly used to describe not only the computers on which each side of the setup sits, but also the programs that are communicating, and also the collection of software components on each of the computers. Throughout this guide, the termsclient andserver are qualified whenever possible to specify which of these meanings is used |