The ALV function groups, SLVC_FULLSCREEN and SALV, use the generic SAP buffering system represented by the package SBUF. When you execute function modules like REUSE_ALV_LIST_DISPLAY or REUSE_ALV_GRID_DISPLAY, the field catalog is buffered in order to increase processing speed. That’s a nice feature that makes a lot of sense in a production environment – after all, field catalogs don’t change that often.
In a development environment however, this feature might mess with your programming activities. If you notice that the ALV table does not change any more according to your changes to the field catalog, execute the program BALVBUFDEL. This deletes the global ALV buffers and makes sure that the ALV table display corresponds to the changes you made again.