Standard Operation

Chapter 1: Introduction

This chapter gives a brief overview of the facilities provided by Fileshare and also describes how Fileshare works.

1.1 Overview

Fileshare is best suited to applications that share data files, concurrently, between many users, across a network. It supports all of the functionality provided by the base COBOL file handling system and provides several additional features:

• Reduced network traffic

• Transaction processing

• Rollforward recovery logging

• Logon and file open security checks

The ability of any one application to take advantage of these features depends on:

• The way the application processes the shared data files

• The type of data files the application shares

• The operating system on which the Fileshare Server is running

• The communications protocol being used between the Fileshare Client and the Fileshare Server

You do not need to make any program source code changes to use the basic Fileshare system. Source code changes are only needed to take advantage of some of the advanced features provided by Fileshare.

1.2 How Fileshare Works

Using the base COBOL file handling system, a typical COBOL I/O request to a shared data file causes the file handler to make several accesses to that data file across the network. See Figure 1-1.

Figure 1-1: Conventional Network

With Fileshare, a program that needs to access a data file has its request processed by the File Handling Redirector (FHRedir) module. The FHRedir module sends the request over the network to a Fileshare Server that performs the low-level I/O operations and then passes the result of the I/O operation, including the file status, back to FHRedir. FHRedir returns the result to the program. See Figure 1-2.

Figure 1-2: Fileshare Network

A Fileshare System is made up of:

Notes:

• The Fileshare Server and the Fileshare Client can be running on the same physical machine. For example, with a multi-tasking operating system such as Windows, the Fileshare Client can run in one session and the Fileshare Server can run in another session. Using this method, you can develop Fileshare applications on a single PC without actually sending data across a network. You should be aware, however, that performance improvements will not be observed, as no network is being used.

• You can also run the Fileshare Server in the same session as the Fileshare Client using the single user mode of operation. This enables you to take advantage of advanced Fileshare features, such as transaction processing, without the need for a network or multiple sessions. For more information on the single user mode of operation, see the section Single User Mode in the chapter Advanced Operations.

Since a single Fileshare Server processes all the requests from several Fileshare Clients, it can use a single copy of the Micro Focus File Handler, regardless of how many users are accessing the Fileshare Server. This has several advantages:

• The Fileshare Server can open the data files exclusively making full use of both its own cache and the operating system's cache

• The Fileshare Server does not need to obtain semaphores on the data file. Normally semaphores are needed to control concurrent access to shared data files.

• The Fileshare Server can process record locks internally without the need to make calls to the operating system

Standard Operation