hI,
SAP Memory
SAP memory is a memory area to which all main sessions within a SAPgui have access. You can use SAP memory either to pass data from one program to another within a session, or to pass data from one session to another. Application programs that use SAP memory must do so using SPA/GPA parameters (also known as SET/GET parameters). These parameters can be set either for a particular user or for a particular program using the SET PARAMETER statement. Other ABAP programs can then retrieve the set parameters using the GET PARAMETER statement. The most frequent use of SPA/GPA parameters is to fill input fields on screens
ABAP/4 Memory
ABAP memory is a memory area that all ABAP programs within the same internal session can access using the EXPORT and IMPORT statements. Data within this area remains intact during a whole sequence of program calls. To pass data
to a program which you are calling, the data needs to be placed in ABAP memory before the call is made. The internal session of the called program then replaces that of the calling program. The program called can then read from the ABAP memory. If control is then returned to the program which made the initial call, the same process operates in reverse.
SAP memory
The SAP memory, otherwise known as the global memory, is available to a user during the entire duration of a terminal session. Its contents are retained across transaction boundaries as well as external and internal sessions. The SET PARAMETER and GET PARAMETER statements allow you to write to, or read from, the SAP memory.
ABAP/4 memory
The contents of the ABAP/4 memory are retained only during the lifetime of an external session (see also Organization of Modularization Units). You can retain or pass data across internal sessions. The EXPORT TO MEMORY and IMPORT FROM MEMORY statements allow you to write data to, or read data from, the ABAP memory.
http://www.sapbrainsonline.com/ARTICLES/TECHNICAL/ABAP/MEMORY/SAP_INTERNAL_MEMORY.html
Regards
Sudheer
