Data files may be stored either as compressed GAMS source or as a GEMPACK-readable Header Array (HAR) file. A HAR file may be examined with the GEMPACK utilities VIEWHAR.EXE or SEEHAR.EXE.
The two file formats provide a trade-off between speed and size. The GAMS-Zip format is used in all GTAPinGAMS computations because it is considerably faster to read. The HAR format, in which subarrays are stored without labels, provides a more compact data format, particularly when the HAR file is further compressed using PKZip or Infozip. A zipped HAR archive for the full GTAPV4 aggregation is 1.6 MB as compared with 4.4 MB for a GAMS-Zip file. The GAMS-Zip format is, however, considerably faster to access (40 seconds versus nearly 3 minutes for dataset GTAPV4).