There is a chance that the older 2.3 executables will run under COBOL Server 5.0 or 6.0 but we strongly recommend that you upgrade the development product to Visual COBOL 5.0 or 6.0 and recompile your application.

The following is from the Visual COBOL 5.0 Release Notes:

Upgrading from earlier Micro Focus products

This version of your product is dependent on a later version of the Microsoft C run-time system than earlier
Micro Focus products. This means that COBOL executables (.exe) built with a version earlier than 4.0
might not be compatible with the current version of the run-time products. If the behavior of your application changes with the current version, we strongly recommend that you relink the main executable with the current version. This will ensure that the COBOL run-time system fully handles any run-time error
conditions that might occur.

A new executable that is fully compatible with the current version can be produced without recompiling the
application, as long as the original object code is available and it is relinked with the current version.
To allow your executables to benefit from the product's latest programming and performance
enhancements, we recommend a full recompilation of your source code.

If you are using Visual Studio, you can configure the IDE to automatically check whether applications
created with older releases must be relinked. If the application uses an older version of the C run-time
system, Visual COBOL can automatically relink the existing executable or .dll to the new version of the C
run-time system without the need to recompile the application first. If a project needs relinking, Visual
Studio displays a message in the status bar providing an option for you to choose and relink the project.