Fifteen minutes is not unusual. For instance, if a SAS job was accessing a file, when the job called to read the file, their would be a pause while the file was read onto disk from tape. If the SAS job was accessing several files, there would be pause for each one. For jobs that require accessing large numbers of files, the command migstage can be used to move files back onto disk prior to them being accessed. It has the form migstage filelist, where filelist is the name of a single file or several files.
Wildcard characters are acceptable.
Doing this prior to a job that will be accessing numerous files on tape will decrease the clock time that a job runs. While just running your job is a fine way to move onto disk the files you need, migstage has the advantage of being able to move in groups of files in a much faster manner.