FLOWOVER
It is default behaviour of the infile statement. Input pointer moves to the next record to fulfil the number of variables used in the input statement if some of the variables are missing in the first line.
MISSOVER
This options prevents the default behaviour mentioned above and prevents the input pointer from moving to the next line and assigns missing values to the remaining variables.
STOPOVER
Stops the data step processing if any of the variable mentioned in input statement is missing.
TRUNCOVER
Its applicable to the last variable; if actual value available in the current record of the external file is shorter than the informat specified, it assigns that ‘Truncated’ value. If it is missing then missing value gets assigned to the variable.