1. Specify the null value. A negative value of the indicator variable specifies the null value. A -1 value indicates that the value that was selected |was the null value. A -2 value indicates that a numeric conversion or arithmetic expression error occurred in the SELECT list of an outer SELECT statement. A -3 value indicates that values were not returned for the row because a hole was detected on a multiple row FETCH. The value of -3 is used only for multiple-row FETCH statements; otherwise, the only indication of a hole is a warning.
2. Record the original length of a truncated string.
3. Indicate that a character could not be converted.
4. Record the seconds portion of a time if the time is truncated on assignment to a host variable.