Index: trunk/ippMonitor/def/README
===================================================================
--- trunk/ippMonitor/def/README	(revision 28614)
+++ trunk/ippMonitor/def/README	(revision 28615)
@@ -161,2 +161,18 @@
 	Regression line is also plotted (correlation coefficient is
 	shown in title).
+
+Plotting with PHP and temporary files
+=====================================
+
+Plots in PHP use temporary files (to provide data to dvo scripts and
+to store result images). Unfortunately, if the files are deleted at
+the end of main php script, the browser does not have the time to
+render the image. If the file is not deleted, they remain in the /tmp
+directory leading to disk space exhaustion.
+
+To avoid this problem, the function delete_old_tmp_files() in ipp.php
+was created. It checks the /tmp directory and removes all files
+belonging to the apache user and that are older than 15 minutes.
+delete_old_tmp_files() is called at the beginning of the
+autocodeImage.php template script (line 4) and is therefore present in
+all generated plotting scripts.