System error: 1: addMetric - Attempted to add duplicate named metric with name requests

#WORKUNIT('name', 'DataGenerationInteger200GB');
IMPORT STD;
// Example: unique_keys :=  20;  // Should be less than number of records
// Example: unique_values := 20; // Should be less than number of records
unique_keys :=  100000;  // Should be less than number of records
unique_values := 10212; // Should be less than number of records
// Example: dataset_name := '~benchmark::graysort1TB'; // dataset_name should be the same in terasort.ecl and should correspond with number of records selected below.
dataset_name := '~benchmark::integer::200GB'; // dataset_name should be the same in terasort.ecl and should correspond with number of records selected below.
// Example: totalrecs := 80; //2030000000 //5000000000
totalrecs := 12500000000; //2030000000 //5000000000
unsigned8 numrecs := totalrecs/CLUSTERSIZE;    // total data size - 203GB
// unsigned8 numrecs := 2030000000/CLUSTERSIZE;    // total data size - 203GB
// unsigned8 numrecs := 5000000000/CLUSTERSIZE;    // total data size - 500GB

rec := {integer  key, integer  fill};
outdata := DATASET(totalrecs, transform(rec, self.key := random() % unique_keys; self.fill := random() % unique_values;), DISTRIBUTED); 

IF( not STD.File.FileExists(dataset_name)
  ,OUTPUT(outdata,,dataset_name)
  ,OUTPUT('Dataset '+dataset_name+' ALREADY EXISTS.')
);