What Is an Application?

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An application is a platform-independent repository for a group of related components, such as procedures, Master and Access Files, data files, HTML files, PDF files, and image files. It provides an area that both confers a unique identity on the application components and facilitates the sharing of components across applications in an organized manner. This construct also simplifies the process of moving a user application from one platform to another and of deploying PC-developed applications.

These components are physically grouped together on an application-by-application basis for run-time execution. This physical grouping can be within an application under a common root or a mapping to an application anywhere in the file system. The physical application or mapped name is referred to as the application name in this document. A comprehensive set of application (APP) commands are provided to control/manipulate the application components, as well as to facilitate applications that can be written and deployed to any platform.

The physical location of an application and its components is determined by a configuration parameter called approot. This parameter is set at installation time and stored in the configuration file edaserve.cfg. On z/OS, the EDASERVE file must be a member in a data set allocated to ddname ERRORS. The default value is dependent on the platform, relative to the install ID home directory, where applicable, as indicated in the following chart.

Application directories can be nested, except on z/OS. A nested application directory is an application created within a higher-level application.

The various operating systems on which the product runs have their own behaviors for physical files and how directories or components are referenced. In addition, some are case sensitive and some are not. For example, on Windows, the files abc and ABC refer to the same file, regardless of how it is stored on disk (aBc, for example). However, on UNIX they are all different files. Additionally, z/OS under PDS deployment and OpenVMS ODS2 make file names uppercase when they are actually saved but they can generally also be referenced in lowercase or mixed case after they have been created. Some operating systems also allow spaces in file names and some do not. To co-exist within the various platforms on which the product runs, the product rules are to either always use APP commands or product tools such as the Web Console to create apps for application files (which will create them in the appropriate case), or to use lowercase names with external tools (such as mkdir myapp and vi mytest.fex), as they will save appropriately and work within the APP framework. Additionally, spaces in file names are not allowed. The use of external tools is also discouraged, as they may not act in the same way as internal tools.

You can change the search path from within your application code. You can also change the search path temporarily to add application names to the beginning or end of an existing search path. APP commands are described briefly in Application Commands Overview and in detail later in this chapter.


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