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 tapesa MARS request is going to access will have an impacton its schedulingon the server. 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. A large number of tapes implies more waiting time.
Additionally users should be aware of the following:
They need to estimate the data volume to be retrieved before issuing a request. It is easy to retrieve Gigabytes of data. Check Try to retrieve a sensible number, up to 20GB per request. You also need to check that computer resources and limits are adequate for the amount of data to retrieve.
They need to estimate the number of fields to be retrieved before issuing a request. Try to retrieve a sensible number, up to 100.000 fields per request.
