1. A computer program product for an operating data center, wherein the data center includes a job tracker, map task trackers, and reduce task trackers comprising a non-transitory storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising: in response to a map task distributed by the job tracker: executing, via a map task tracker, the map task to generate a first map output having first version information, wherein the first version information includes a version value identifying when the map task was added and is assigned by the map task tracker, and wherein the executing further comprises: receiving from the job tracker the map task, the map task specifying storage positions for input data splits of the map task; reading the input data splits from the storage positions included in the map tasks; analyzing the input data splits to generate key-value pairs; assigning a version value to each of the key-value pairs; executing, with a map function, a map operation on the key-value pairs having the version value to generate intermediate key-value pairs having the version value; executing a partition operation on the intermediate key-value pairs to generate the first map output; storing, via the map task tracker, the generated first map output; informing, via the map task tracker, the job tracker of the map task completion; and transmitting, via the map task tracker, to the job tracker, related information of the first map output, in order for the job tracker to provide the map output to the reduce tracker, wherein the related information comprises a job number, a map task number, and the first version information; in response to a reduce task distributed to a reduce task tracker by the job tracker including the related information: acquiring, via the reduce task tracker, one or more map outputs for key names having specified version information from the map task tracker, wherein the acquired one or more map outputs comprise one or more current map outputs having the first version information and one or more historical map outputs having historical version information, wherein the historical version information indicates origination of the key names from a historical map task added prior to the map task, wherein the specified version information defines a range of the map outputs required for the reduce task including the first version information; and executing, via the reduce task tracker, the reduce task on the acquired one or more map outputs.