QSAM

from The Free On-line Dictionary of Computing (8 July 2008)

Physical Sequential
QSAM
Queued Sequential Access Method

   <file format> (PS, QSAM, Queued Sequential Access Method) The
   simplest {data set} on an {IBM} {mainframe}.  Sequential files
   can only be read or written from the beginning: they do not
   support {random access}.

   [Why "Queued"?]

   (2003-12-05)