Run Number Mapping (ORN's and URN's)

Each file written by the DAQ system is assigned a run number, which is recorded in the FILEH buffer. Unfortunately, we got during the experiment a couple of files with duplicate run numbers, ending up with two files having the same run number in the header.

Clearly, it is neccessary to have a unique identification for each file. The original run numbers encoded in the file headers can't be used for this purpose because they are ambiguous in some cases. To resolve this, a unique run number has been assigned to each file. The unique run number (URN) is in most cases identical to the original run numbers (ORN) but mapped to some unique value in cases of conflict.

Conflicts are usually solved by assigning a URN in the range of 1000-2000. A consequence of this is, that three runs taken in one after the other have non-contiguous URN's, like 4023, 1023, and 4024. This has to be kept in mind when one wants to process intervals of runs.

IMPORTANT NOTE: The file header always contains the original run number. So programs, which use the run number from the file header will always use the ORN and not the URN. There is clearly some potential for confusion.

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Last update: 23-Jul-1998
Walter F.J. Müller