Advanced Server Technology

	• Advanced Server Technology • Features of AST • Advantages of the AST Approach • Technology Overview • Contact Us for More Information

Features of AST

• Responds to client requests on a first-come, first-served basis
• Retrieves data and returns data to client programs via data queue technology
• Processes from 1 to 99 records at a time for the client program
• Employs both full and partial key positioning and retrieval methods: chain, read, read equal, read prior
• Validates existence of a record in the database without retrieving the data

• Performs data validations and enforces business rules so client programs can focus on display management
• Efficient use of network resources as the server programs return only the data requested by the client in variable length message packets
• Returns message text and message id for all errors detected to the client program, for simplified error management at the client
• Updates, then retrieves next record, with one message call to the server program for efficient client code
• Automatically tests to ensure that another client program has not updated the data since retrieved by the client

Advantages of the AST Approach

Saves time and development energy for over-burdened development staffs, helping you stretch your applications support budget.

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Technology Overview

The DB2/400 database server programs operate in subsystem SMMSIO, which is started with every IPL and checked periodically by SMMS user jobs. The database servers use data queues to exchange information with client programs. It does not matter whether these client programs are running on a PC workstation or in the “green screen” environment.

Figure 1 shows the system in a “wait state”. The server program is a “never ending” program running on the iSeries/400. It receives data requests from all client programs via the “Server Data Queue”. There is one server program for each database file in the SMMS database.

Figure 1


The server program also enforces SMMS business rules. All client requests to add, change or delete data are verified by the server program before the database update can take place. This ensures that database validations will be consistently enforced.

Figure 2 (below) shows what happens when the client program requests data. The client program sends a request to the server program, via the server’s data queue. As soon as the client program sends the request to the server, it monitors it’s own data queue waiting on data to be returned from the server. Meanwhile, the server program receives the data request and gets the data from the database.

Figure 2


Figure 3 shows what happens when the server program responds to a data request from the client. The server program receives the information request via its data queue, and fetches the requested data from the database. The data is returned to the client program via the client program’s data queue. As the client program receives the data, it is able to display the data onto the screen.

Figure 3


The result is that all client programs --- browser, green screen or windows-based --- are served data on a “first come, first served” basis. System business rules are enforced equally, as the server programs also perform edits and validations before database changes are allowed, again whether the source of the data is “green screen” or windows.

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Contact Us For More Information

If you’d like more detailed information on this technology, we have a technical “white paper” available free of charge to interested parties. You may download this paper immediately, in Acrobat PDF® format, by clicking here.

Or you can get a printed copy by filling-out our contact form.

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