SAP SHM CLASSES

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ABAP_SHM - Classes and Interfaces
The hierarchy of global classes that are involved when working with shared objects is as follows:
CL_ABAP_MEMORY_AREA
|
|--CL_SHM_AREA
| |
| |--Area Classes
|
|--CL_IMODE_AREA
The meaning of the three predefined system classes:

CL_ABAP_MEMORY_AREA is the superclass of all area classes.

CL_SHM_AREA is the superclass of all user-defined area classes.

CL_IMODE_AREA is a predefined area class for the ABAP_ISESS .
There is also a system interface that must be implemented by the class for the optional area constructor:
IF_SHM_BUILD_INSTANCE
|
|--Area Constructor Class