Difference between CMOD and SMOD

SMOD is the actual enhancement. This transaction allows you to create an ENHANCEMENT, which you will include in a PROJECT, by identifying its COMPONENT(S). In the case where SAP has already created an ENHANCEMENT for its pre-defined user-exits, you will not need to use transaction SMOD; instead, you should just use transaction CMOD.

SMOD is the transaction which allows you to create an enhancement, which will be included in a project by identifying its components. In case where SAP has already created an enhancement for its predefined userexit you just need to use CMOD.

CMOD is the grouping of all SMOD's. This transaction allows you to create a PROJECT by identifying its ENHANCEMENT(S). After determining all of the ENHANCEMENTS that are part the

PROJECT, you will have to activate the PROJECT. You will still need to code your user-exit; therefore, you may want to wait until this step is completed before activating the PROJECT.

CMOD allows you to create a project by identifying its enhancement. After determining all of the enhancements you will activate the project.

You determine which enhancements should be included in a particular project using transaction CMOD. SAP comes with standard enhancements that include various user-exits. However, if these user-exits do not involve a transaction activity that you want to modify, you will have to create your own user-exit and enhancement using
transaction SMOD.