Currency in IDMS is the most recently accessed record by the application programs. In other words currency is the current position where you are in the database.
IDMS maintains 4 types of currencies : Run Unit, Record Type, Set and Area.

RUN UNIT Currency: Most recently accessed record by the program

RECORD TYPE Currency: Most recent record occurrence accessed for each record type

SET Currency: Most recent record occurrence accessed in each set, either the owner or the member.

AREA Currency: Most recent record occurrence accessed in each area accessed by the program.