Index: openacs-4/packages/acs-tcl/tcl/acs-cache-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-tcl/tcl/acs-cache-procs.tcl,v
diff -u -r1.10.2.11 -r1.10.2.12
--- openacs-4/packages/acs-tcl/tcl/acs-cache-procs.tcl	28 Oct 2020 15:39:19 -0000	1.10.2.11
+++ openacs-4/packages/acs-tcl/tcl/acs-cache-procs.tcl	6 Dec 2020 08:43:59 -0000	1.10.2.12
@@ -381,18 +381,23 @@
     #
     # The per-thread caches use namespaced variables, which are not
     # touched by the automatic cleanup routines of the server. So, the
-    # values cached in one requests can be used by another
-    # requests. These per-thread caches are kept as long the thread
-    # lives, there is so far no automatic mechanism to flush
-    # these. So, these are typically used for values fetched from the
-    # database, but which not not change, unless the server is
-    # restarted.
+    # values cached in one requests can be used by some later request
+    # in the same thread. The entries are kept in per-thread caches as
+    # long as the thread lives, there is so far no automatic mechanism
+    # to flush these. So, per-thread caches are typically used for
+    # values fetched from the database, which do not change, unless
+    # the server is restarted.
     #
-    # Per-request caches have very short-lived. Some values are needed
-    # multiple times per request, and/or they should show consistently
-    # the same value during the request, no matter, if concurrently, a
-    # value is changed (e.g. permissions).
+    # Per-request caches have very short-lived entries. Some values
+    # are needed multiple times per request, and/or they should show
+    # consistently the same value during the same request, no matter,
+    # if concurrently, a value is changed (e.g. permissions).
     #
+    # Note: the usage of per-thread caches is only recommended for
+    # static values, which do no change during the life time of the
+    # server, since there is so far no automatic measure in place to
+    # the flush values in every thread.
+    #
     ##########################################################################
     nx::Class create acs::LockfreeCache {
         :property {prefix }