Concurrent Import Sets are not created even if the "Concurrent Import" option is selected on the Scheduled Import Set record. The import is carried out in with classic Import Set with a single thread, and no information / feedback is provided to the instance administrator about why it is being carried out this way.
Steps to Reproduce
1. Open the OOB Import Set Transformer Scheduled Job:
2. Navigate to the link:
3. Set the System ID field of these jobs to 'None'.
4. Try to run a scheduled import with Concurrent import set as true. Observe the import runs in a classic way instead, with no feedback given to the administrator.
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Aside from avoiding to'set the System ID field to 'None', there is no workaround available at this time.
Related Problem: PRB1367526