A conversion can cause an overflow error if the precision of the target data type is smaller than the corresponding precision for the source data type.
If the least significant value of the source is lower than that of the target, then those source values having lower precision than the least significant field of the target are ignored. The result is truncation. Recovery from this action is installation-dependent.
If the most significant field in the source value has higher significance than the most significant field in the target value, then the higher order fields of the source are converted into a scalar value of the precision of the most significant field in the target, using the factors of 12 months per year, 24 hours per day and so on.
If the compared scalar value overflows the defined precision for the target field, an error is returned.