Oracle Error Codes

column to be modified must be empty to decrease precision or scale

An ALTER TABLE MODIFY statement attempted to decrease the scale or precision of a numeric column containing data. In order to decrease either of these values, the column must contain only NULL values. An attempt to increase the scale without also increasing the precision will also cause this message.

How to Solve :

Set all values in the column to NULL before decreasing the numeric precision or scale. If attempting to increase the scale, increase the precision in accordance with the scale or set all values in the column to NULL first.