For OS/390, a dual load module configuration exists when a set of classes is packaged with a Smalltalk virtual machine to create a single load module that is intended to be used by other separately packaged Smalltalk applications. This chapter uses the following terms to describe the separate components of a dual load module configuration:
For OS/390, only one dependent load module can use the classes of only one base load model at the same time. You can build several dependent load modules that share the classes of one base load module, but that base load module can only be used by one dependent load module at a time. Further, more than one base load module can exist across a set of applications in a given environment, though each dependent module can share the classes of only one base load module.
The figure below illustrates the relationship among dependent and base load
modules for MVS (or OS/390).
By packaging a set of classes in a base load module that are common to multiple applications, you can realize some benefits:
Though the content of a base load module is completely determined by the needs of an installation, likely candidates include the Smalltalk Kernel and central feature classes such as the CICS, IMS, OS/390 Native, or DB2 access classes. Other candidates for the base load module are any classes that are determined to be common across a certain set of applications.
Arriving at the correct mix of shared and nonshared classes will generally require an understanding of the applications and will require evaluation and planning to determine an optimal configuration for a given installation's application environment.
Note that if a class exists in a base module, it cannot be extended with
any of the following methods into a dependent module:
+ | - | < | <= | > |
>= | = | ~= | == | // |
\\ | * | / | \ | & |
at: | at:put: | value | value: | not |
new | new: | size | value:value: | class |
between:and: |
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