dpack takes a list of one or more isam files and will rebuild each in turn. It works by building a temporary copy of the original file and copying all active data records to it, then deleting the original and renaming the working copy.
The temporary file is created in the same directory as the original and is named dpnnnnn, where nnnnn is the current process id.
You must ensure that you have write permission on the data directory and that there is enough room for dpack to build the working copy.
dpack will fail if it cannot obtain an exclusive lock on the file.