Natural Development Server Version 8.2.5 for BS2000/OSD
 —  Natural Development Server for BS2000/OSD  —

Natural Development Server on Mainframes

This document describes the concept and the architecture of the Natural Development Server (product code NDV) which is designed for use under SMARTS on BS2000/OSD.

The following topics are covered:

Development Server Concept

A Natural Development Server is a multi-user, multi-tasking application. It can host Natural sessions for multiple users and execute their requests concurrently.

The concept is based on the "serverized" Natural runtime system. Its architecture comprises a server front-end stub (development server stub NATRDEVS) that uses the Natural front-end to dispatch Natural sessions and to execute functionality within these sessions.

The Natural remote development server architecture basically consists of:

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NDV under SMARTS on BS2000/OSD

SMARTS is an acronym for "Software AG Multi-Architecture Runtime System". It constitutes a runtime layer that allows POSIX-like applications to run on mainframe operating systems. Software AG products communicate with the operating system through the SMARTS layer.

SMARTS on BS2000/OSD Basics

SMARTS implements a server runtime environment for the execution of the NDV server. Technically, SMARTS represents a C runtime system and implements a nearly full-blown POSIX system. It drives a family of tasks which either process dedicated functionality or process the application payload in parallel-executed worker tasks. The tasks with a dedicated functionality are the main or oc task, the system thread loop task (started as second task), the socket communication task, the pfs task and the sequential file IO task. The pfs task is optional; it processes all IO operations on the POSIX file system (PFS). The PFS is used for NDV work/print file access method, thus allowing the testing of programs which execute access to work or print files.

SMARTS offers a configurable set of resources to process the application workload. These resources are mainly threads and (worker-) tasks. The actual workload is scheduled by the SMARTS kernel using these resources. In case of momentary shortages of one or the other resource, SMARTS is able to queue incoming requests and to roll-out inactive threads.

All data, processed by SMARTS or a SMARTS application, is located in one common memory pool, the data pool. All code modules, except for some smaller bootstrap routines, are loaded as shared code into another common memory pool, the code pool.

The worker-tasks are the processes (TSNs) by which the Natural runtime is executed. The amount of storage requested by Natural is located in the SMARTS threads within the data pool during the execution of a transaction. If the number of sessions to be processed exceeds the number of threads defined, an internal facility is invoked for rolling the threads. Threads rolled out are placed in compressed format in a so-called roll bufferpool which resides in the data common memory pool as well.

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Front-End Stub NATRDEVS

The multi-user, multi-tasking, front-end stub NATRDEVS is launched to initialize a Natural Development Server.

The following topics are covered below:

Stub Description

The task executing the server initialization (TMain) basically is the main listener which waits for incoming requests from the remote development client (Natural Studio). It owns a session directory to manage multiple clients (users) and their corresponding remote Natural sessions. TMain has the task to accept all incoming requests and to dispatch them to other subtasks (TWork). The process is as follows:

That is, each client owns one subtask TWork on the Natural Development Server and multiple remote Natural sessions (one for each mapped environment). This subtask remains active as long as the mapped environment on Natural Studio is the currently active environment. Each remote Natural session remains active until the user disconnects/unmaps the corresponding environment on the client side. Consequently, a Natural session can be executed under different subtasks if the user switches among multiple environments.

Natural System Variables Used

Within a Natural Development Server session, the following Natural system variables are used:

Natural I/O Handling

The Natural runtime system allows I/O execution in the same way as in an online environment:

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The front-end is called (together with the Natural runtime system) by the front-end stub for session initialization/termination, request execution and session roll-in/roll-out.

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Transaction Processors

The transaction processors are Natural programs in the library SYSLIB that process transactions (for example, "save source", "get library list") requested by the remote development client. The transaction processors are invoked by the front-end stub.

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Gateway Module

The gateway module NATGWSTG is already included in the Natural nucleus.

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Server Monitor

To enable the administrator to monitor the status of the Natural Development Server, a monitor task is provided which is initialized automatically at server startup. Using the monitor commands, the administrator can control the server activities, cancel particular user sessions, terminate the entire server, etc. See Operating the Development Server.

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Product Interaction

The following figure illustrates the interaction of Natural Studio used as a remote development client with a Natural Development Server.


  1. Natural Studio (the client) sends a remote development request to the Natural Development Server (NDV) using the port number specified with the NDV configuration parameter PORT_NUMBER.

  2. The Natural Development Server dispatches the Natural session using the Natural front-end you have specified with the NDV configuration parameter FRONTEND_NAME (NCFSERV in this example).

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