D provides two basic types of variables for use in your tracing programs: scalar variables and associative arrays. This chapter explores the rules for D variables in more detail and how variables can be associated with different scopes. A special kind of array variable, called an aggregation, is discussed in Chapter 3, Aggregations.
Scalar variables and associative arrays have a global scope and are not multi-processor safe (MP-safe). It means that the value of these variables can be changed by more than one processor and thus there are chances that the variable can became corrupt.
Aggregations are MP-safe even though they have a global scope.