A variable's record variance specifies whether or not the variable's values change from record to record. The effect of a variable's record variance is defined as follows.
The values do change from record to record. Each variable record is physically written with no gaps between records (i.e., if a record more than one beyond the maximum record is written, the intervening records are also physically written and contain pad values). If a record is read beyond the maximum record written to a variable, the pad value for the variable is returned. Variables of this type are referred to as record-variant (RV).
The values do not change from record to record. Only one record is physically written to the variable. Each record contains the same values (including virtual records beyond the first record). Variables of this type are referred to as non-record-variant (NRV).
Section 2.3.8 describes variable records in more detail.
A variable's record variance is specified when the variable is created. The record variance of an existing variable may be changed only if values have not yet been written to that variable. (An explicit pad value may have been specified however.)