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(lightbulb) The idea is to request as much data as possible from the same tape file or to reduce the number of tapes involved.

  • The number of tapes a MARS request is going to access will have an impact on its scheduling on the server. 
  • A large number of tapes implies more waiting time.
  • As a rule of thumb, two or more separate requests accessing files on different tapes are scheduled more efficiently than a single request accessing two or more tapes.

(warning) Additionally users should be aware of the following:

  • The data volume to be retrieved should be sensible, up to 20GB per request.
    (grey lightbulb) Check that your computer resources and limits are adequate for the amount of data to retrieve.
  • The number of fields to be retrieved should be also a sensible number, up to 600.000 fields per request.

More details and examples:

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