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The OM chains fail saying that an OM exposure mode is "UNDEFINED" in the ODF. However, ...

It might happen that when running omfchain, omichain, or omgchain, an error message as the following appears, and processing of the corresponding data stops:

** omprep: error (NoSuchExposure), Tried to access an exposure of instrument `OM' in mode `UNDEFINED' but there is none in ODF `/home/myusername/Data/U11763/ODF' omichain:- omprep has detected an error- this observation will not be processed

You check everything, and the data are there and all seems to be in order. What has happened??

Well, check the whole path of your ODF location in the SAS summary file. In the above example:

/home/myusername/Data/U11763/ODF

If you have in your path strings like Sabc or Uabc or Xabc, where a, b and c are digits (0 to 9), then this is the reason for the failure.

This behavior is produced by the way file names are handled into some OM SAS tasks. This is an error, and it will be corrected in the next SAS release. Meanwhile, remember: avoid having in your path to the data strings of the type Sabc or Uabc or Xabc as defined above, e.g.: S010 or U123 or X567.