Indicator variables can be used with main variables intended for I/O, although certain indicator variables cannot be used for input (for example, in a WHERE clause).
PP2 uses indicator variables to show nullness of a field sent to or returned by the database, as well as truncation of a character or byte string when placed into the corresponding main variable.
Indicator variables are documented in Teradata Vantage™ - SQL Stored Procedures and Embedded SQL , B035-1148 .