The TSM API return codes are documented in the TSM API manual and the Messages manual. Return code 106 has two possibilities, both resulting from general inability to access the file system object to be worked with.
A TDP straddles the TSM API and the API of the application it was written for. When the TDP has problems accessing data, one needs to review the conditions under which it is run relative to what it needs, and any messages within the application corresponding to the TDP's access attempt. The latter may require the assistance of site experts for that application. Richard Sims