The recursive subprogram is the one that calls itself. Think of a recursive call as a call to a few other subprograms that does the similar task as your subprogram. Each recursive call creates a new illustration of any items declared in the subprogram, involving parameters, cursors, variables, and exceptions. Similarly, the new instances of the SQL statements are created at each level in the recursive descent.
Be cautious where you place a recursive call. If you place it within a cursor FOR loop or between the OPEN and CLOSE statements, the other cursor is opened at each call. As a result, your program may exceed the limit set by the Oracle initialization parameter OPEN_CURSORS.
There should be at least two paths through a recursive subprogram: one that lead to the recursive call and one that does not. At least one path should lead to a terminating condition. Or else, the recursion would (theoretically) go on everlastingly. In practice, if a recursive subprograms stray into vast regress, the PL/SQL eventually runs out of memory and raises the predefined exception STORAGE_ERROR.