Rational Programming Patterns for System z

The Server Dialog or Server entity

The purpose of these entities is to develop and generate the server-side components of Pacbench C/S graphic or TUI applications.

The Server Dialog is a logical envelope which groups the various server components of an application.

In the Server Dialog, you give the general characteristics of the application. You specify the generation variants and options which apply by default to all the attached components.

Two basic types of architecture are possible: one which uses a monitor, and the other which does not.

The Business Component

A Business Component supports a set of services on a Logical View.

These services can be generic and dedicated to selections and updates on a Logical View. They can also be specific and support functional requirements.

The Business Component must perform the processing associated with the selection, check, and update services requested by the Logical Views. This processing includes:
  • Access to the external resources (files, databases),
  • Checks and updates,
  • Specific processing (calculations, extraction methods...),
  • Error management.

Generic services are independent of the storage medium used to manage their persistence.

A Business Component then describes the relations between a Logical View and the persistence objects used to select or update its instances.

The server monitor

This monitor, reserved for TUI applications. performs the following tasks. It:
  • Receives the information sent by the client using the communication area,
  • Calls the server which corresponds to the service requested by the client,
  • Returns the information to the client monitor.

The communication monitor

This monitor, reserved for graphic applications, performs the following tasks. It:
  • Handles the communication functions (message sending and receiving) according to the target environment.
    Note: If an application is run on different environments, there must be as many communication monitors as there are environments. Several communication protocols can be used for the same environment (example: CICS ECI and CICS CPIC).
  • Checks each received message.
  • Sends and receives the query.
    Note: According to the size allowed for the physical message, several physical messages can be issued in order to obtain the complete logical message. A work file must therefore be available for a temporary storage of the current query.
  • Sequentially processes the services included in the query by calling the appropriate Services Manager.
  • Handles the transactional management (COMMIT/ROLLBACK)

    The communication monitor uses the COMMIT and ROLLBACK services of a database or of a transactional monitor, depending on its generation variant.

    The server part runs a COMMIT or a ROLLBACK, according to the error context (protocol error or application error) established at the end of the query processing. If an error occurs, the query processing is stopped and an error message is sent. All the resources used by the query processing are then made available after the response has been sent.

The error message server

The error message server generates the messages associated with the errors detected by the Business Components. These messages are stored in a dedicated and generated file.

The initialization/termination Business Component

An initialization/termination Business Component is used to implement specific procedures before and after the execution of a request associated with a Folder.
Note: This function is then only available for graphic applications which use a Folder.

An I/T Component is called by the Services Manager before the first call to the Business Component associated with the request and after the last-executed Business Component.

It is available either for an initialization or for a termination process.

For an initialization process, the only data that can be processed in input is that sent by the client component through the user buffer.

An I/T Component is used to run the services associated with all the Business Components of a Folder.

Therefore, the generation of an I/T Component contains the access functions and PERFORM which correspond to the services associated with all the Business Components of a Folder.

Each service associated with a node uses specific parameters in input and produces results defined in the WORKING-STORAGE SECTION of the I/T Component.

Generation

For the instances imported from Pacbase, the skeleton language of the local generation is identical to the Pacbase skeleton language. This piece of information is retrieved from the extraction of the Pacbase models and from the import. It is stored in the Library.


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