An indicator variable is a two-byte integer.
See the entry for the SMALLINT SQL data type in Table 1.
An indicator structure can be defined by declaring the variable as an array with an element length of 4,0 and declaring the array name as a subfield of a data structure with B in position 43. On retrieval, an indicator variable is used to show whether its associated host variable has been assigned a null value. On assignment to a column, a negative indicator variable is used to indicate that a null value should be assigned.
Indicator variables are declared in the same way as host variables and the declarations of the two can be mixed in any way that seems appropriate to the programmer.