@cmd{ADD FILES}, @cmd{MATCH FILES}, and @cmd{UPDATE} commands. The
following sections describe details specific to each command.
-Each of these commands reads two or more input files and combines
-them. The command's output becomes the new active dataset. The input
-files are not changed on disk.
+Each of these commands reads two or more input files and combines them.
+The command's output becomes the new active dataset.
+None of the commands actually change the input files.
+Therefore, if you want the changes to become permanent, you must explicitly
+save them using an appropriate procedure or transformation (@pxref{System and Portable File IO}).
The syntax of each command begins with a specification of the files to
be read as input. For each input file, specify FILE with a system
system-missing value for numeric variables or spaces for string
variables.
+These commands may combine any number of files, limited only by the
+machine's memory.
+
@node ADD FILES
@section ADD FILES
@vindex ADD FILES