what is the difference between set and get parameters.
When a user or an application (e.g. via RFC) logs on to an SAP system, he, she, or it connects to a certain application server where a User Session is created. The common memory of a User Session is the so-called SAP Memory. ABAP programs have access to SPA/GPA parameters stored in the SAP memory. SPA/GPA parameters (or SET/GET parameters) are set using SET PARAMETER and read with GET PARAMETER. Input fields on Dynpro screens can be linked with SPA/GPA parameters. When a screen is called, the default values of such input fields are taken from the SAP Memory. When the screen is left, the field values are stored in SAP Memory (thats why you always find the name of the last edited program in the input field of the ABAP Editor SE38). SPA/GPA parameters are managed in the database table TPARA.