Jonathan Lewis discusses his experience with automatic SGA sizing. I have an Oracle10g database that utilizes automatic SGA sizing. I have not experienced any problems to date, however this installation used by a development team is small and surely doesn’t see a high amount of activity other systems might.
Jonathan also provides a script he “hacked together” to query the v$sga_resize_ops view displaying the history on how the SGA components have been re-sized since the last instance startup.
Jonathan Lewis recently provided some updated updated information on this subject on his blog – SGA Resizing.