The development of the information systems has achieved high results nowadays. There are many examples of database management systems that can be successfully used for the corporative business environments; Informix is one of the best solutions in this area. If you need to find stable and reliable software for the database server, then you should pay attention to Informix.

There are strict requirements for a server computer that should be used as a base for the enterprise information infrastructure: a high performance, scalability, mixed loading of computer servers with different type tasks and an interrupting access to the data. The Mechanism Informix OnLine Dynamic server meets all these requirements.

The Informix OnLine Dynamic server has a dynamic scalable architecture (DSA). It means that existing server computer processes (virtual processors) distribute services for their clients.

A virtual processor is a database server process. You can compare a virtual processor with an operation system. There are different types of specialized virtual processors:

CPU - threads that perform the clients requests optimization;

AIO - asynchronous data exchange with the disk;

ADM - administrative functions, such as a system timer;

TLI - control of the network interaction by TLI interface (Transport Layer Interface).

The initial number of virtual processors of each class that are created at each run of the Informix - OnLine DS is set in the configuration file. However, the administrators of the server computer are not always able to predict if some certain virtual services are required by the system. Administration tools allow to start an additional virtual processor. For instance, if a number of the required CPU processors is growing up in order for the systems to start the additional virtual processors. In this way, the server can add the virtual processors of the AIO, ADM and TLI classes.

The older models of the Informix built an individual server process for each user. The new model 7.1 has new principles of work; consequently, it has some advantages:

- Decreasing of the operation system loading (there are not many server computer processes);

- Decreasing of the clients’ needs in the operative memory;

- Optimization of the system resources sharing;

- Rational planning of the processes and priorities assigning.

Informix provides some additional features for the multi-processor platforms:

- Uniform loading for different processors;

- Enforcing of the complex queries handling by the parallel execution at several processors.

The architecture DSA uses all the possibilities, provided by the symmetric multiprocessing systems and it can work at one processor systems as well. The developers of the software suppose to extend the server architecture in the following releases. All basic DSA technologies are built-in and are included to the server libraries. The usage of these technologies does not depend on the operation server.

Informix - OnLine DS is a multi-threading system; each client has a separate sub-task, performed within a server process, called thread. Sometimes, the server generates some parallel threads to handle one client request. The threads are constructed to perform internal tasks of the server. Informix OnLine - DS relies on the threads mechanisms that are accessible in some operation systems. It forms threads that are specific for handling database procedures.