One regular issue that DsView users raise with us is that data set files are locked while DsView has them open. This is a side-effect of the way the data set reader engine was originally written - it was first written for dsread, which tends to open a data set for a short time while converting it to CSV/SQL and then closes it again.
The next release of DsView will be versio 0.4 and will be out soon to remove this restriction - data set files will no longer be locked while DsView has them open, and you will be able to re-run programs etc without any locking issues. DsView will notify you if a data set has been modified on disk and you will have the option to close it or to re-open it to see the new version. Very large data sets will still be supported, even if they're too big to fit in the physical memory in your machine.
All feedback welcome as usual, please let me know of any other issues or new features you'd like to see as DsView develops!