Interoperability with IBM Host Systems
Interoperability with IBM Host Systems |
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SNA Server provides host-connectivity services for Web-based users in several ways. The following Web-to-host solutions are commonly adopted by enterprises:
The following sections detail options for deploying SNA Server in each of these scenarios and describe the environments in which each is best deployed.
Using a Web browser to provide access to host applications through a traditional 3270 or 5250 terminal interface is a simple and effective way of providing terminal access to your users. This Web-to-host solution is ideal if your user base is already familiar with the character-based terminal interface and is adept at using existing host applications. In most environments where this solution is deployed, existing host access technology is already in place, either through dumb terminals or software-based emulators.
SNA Server can provide browser-based terminal emulation through the deployment of SNA Server Web Client, as shown in Figure 10.33. SNA Server Web Client provides terminal emulation features through an ActiveX control that is part of a package downloaded to a user's browser from a Web server such as IIS. Once downloaded and invoked, the control establishes a connection with the sponsor SNA Server computer that provides a connection to the host system.
Figure 10.33 SNA Server Web Client Terminal Access Installation
Using this method, no configuration is required on the client workstation because all connection information is specified by the administrator before SNA Server Web Client is downloaded into the browser. When a user downloads the ActiveX package, the connection information is contained in the download, allowing SNA Server Web Client to automatically establish a connection to the host system.
Once SNA Server Web Client software is downloaded to the client workstation, it does not need to be downloaded again unless the browser detects a newer version of the software on the Web server; this can speed up the client startup time and minimizes the load on your server. Because SNA Server Web Client software is distributed from a central location, updates and changes to host configurations are easily propagated to your users the next time they start the SNA Server Web Client application.
SNA Server Web Client is currently available for Windows NT, Windows 2000, Windows 95, and Windows 98–based clients running Internet Explorer 3.02 or later. Both 3270 and 5250 terminal emulation clients are provided.
Complete information about configuring and installing SNA Server Web Client is provided in the SNA Server version 4.0 documentation.
As mentioned earlier, host systems are ideal platforms on which to provide large-scale database services for enterprises. Using SNA Server, Web technology can extend host database access to a broader range of users.
A common way to integrate Web technology with host databases is to use the rich-text capabilities of HTML to create visually appealing, user-friendly interfaces for character-based host database systems.
For example, a Web browser could be used to collect database queries on an HTML form. The queries could then be transferred, using ISAPI or some other common gateway interface, from the Web server to a service that can communicate with the host database system. The results of the query could then be formatted into HTML and viewed through the user's browser.
SNA Server is an ideal tool for deploying Web-to-host data access solutions because it can provide host database access without the need for host code or a modified database system. Using a feature such as OLE DB Provider, you can extend a wide range of services to Web users. Figure 10.34 illustrates how different data access components integrate with SNA Server and other services to provide access to host data files from a Web browser.
Figure 10.34 Web Access to Host Data File System
In the browser, the user loads and inputs data into an Active Server Page (ASP) hosted by the Web server (IIS). The ASP then sends the data through the ActiveX Data Objects (ADO) interface to the OLE DB Provider feature of SNA Server.
In this scenario, the OLE DB Provider uses the APPC record-level input/output (RLIO) protocol of the IBM Distributed Data Management (DDM) architecture (level 2 and higher) to communicate with the host database. This entire process is transparent to the host system and to the user.
The SNA Server OLE DB Provider is implemented as a source DDM requester and is interoperable with target DDM server implementations on most popular host environments, including MVS/ESA, OS/390, and OS/400.
A Web browser can also be used to access TPs that operate on a mainframe, such as CICS or IMS applications. Using SNA Server's COMTI feature, you can develop client/server applications that use Web browsers to interact with mainframe transaction systems. Because CICS programs can access DB2 databases, COMTI can also provide programmatic access to DB2 on a mainframe.
You can use any technique for accessing COM objects from the browser because COMTI creates a standard COM Automation server component that acts as a proxy for the mainframe CICS or IMS TPs. Figure 10.35 illustrates the components that could be involved in creating a Web application that uses server-side scripting to dynamically create objects and invoke methods.
Figure 10.35 Web Access to Host Transaction System
Other applications that use technologies such as Remote Data Services (RDS) and client-side scripting can also be developed. In these scenarios, object creation and method invocation are launched from a client script executed on the server and the RDS control directs records back to the client over HTTP. Retrieved records can then be bound to an HTML grid control for display purposes.
For more information about sample applications that use these Web-to-host technologies, see the samples folder on the SNA Server CD.
