The caller must provide the mechanism for closing the files by periodically calling unmaparr to close all open files. In the event of failure, no data is returned, and there are a variety of error codes. A pound sign causes the rest of the line to be ignored. The reading routine for the traces will generally not complain, regardless of errors in the waveform file. The ascii format is intended primarily as a debugging and portability tool, not for serious work.
Performance is likely to be slow.
These names are not qualified, however, so you must arrange, for instance, that dbgetv of time gets time from the wfdisc table, not the sensor table, probably by making wfdisc the first table in the join.