.TDM file and .TDX are pair, and .TDM referenced .TDX file name internally. So, If you changed the name of .TDX file name, there is no way could reference the .TDX from .TDM. But, if you changed the .TDM file name only, you could still access this file. Because, the original reference name wasn't changed.
If you wanted to changed the name of the .TDM file, you could load and save the file again with different name in DIAdem. In DIAdem NAVIGATOR, click the Save Data File As. Then, you can save data loaded in data portal as the name what you want.
Basically, use the .TDMS rather than .tdm file format, if you could. Because, .TDM needs necessary pair file, .TDX which includes raw data. So, if either file is lost, there is no way to recover it. But, TDMS saves both the raw data and the meta data in one file, so there is no problem with changing name of the file alone. If you used DIAdem, you could saved file in DIAdem NAVIGATOR both format .TDM and TDMS.
More about the strucutre of .TDM and TDMS, refer this document (LabVIEW 2018 help-TDM versus TDMS)
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