Randomization of random variables declared using rand and randc keywords within a class can be disabled and will not be randomized. This is done using the method rand_mode(), which is very similar to the constraint_mode() method used to disable constraints. So a disabled random variable is treated the same as if they had not been declared rand or randc.
The object is any expression that yields the object handle in which the random variable is defined, and random_variable is the name of the random variable to which the operation is applied. If random_variable is not specified (only allowed when called as a task), then all the variables will be subject to the operation.