diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 7554cba3f9..b8e32d765b 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -4147,7 +4147,8 @@ ANY <replaceable class="parameter">num_sync</replaceable> ( <replaceable class="
         used. When setting this parameter you should consider both
         <productname>PostgreSQL</productname>'s shared buffers and the
         portion of the kernel's disk cache that will be used for
-        <productname>PostgreSQL</productname> data files.  Also, take
+        <productname>PostgreSQL</productname> data files, though some
+        data might exist in both places. Also, take
         into account the expected number of concurrent queries on different
         tables, since they will have to share the available
         space.  This parameter has no effect on the size of shared
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 2317e8be6b..e471d7f53c 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -2987,10 +2987,9 @@ static struct config_int ConfigureNamesInt[] =
 
 	{
 		{"effective_cache_size", PGC_USERSET, QUERY_TUNING_COST,
-			gettext_noop("Sets the planner's assumption about the size of the disk cache."),
-			gettext_noop("That is, the portion of the kernel's disk cache that "
-						 "will be used for PostgreSQL data files. This is measured in disk "
-						 "pages, which are normally 8 kB each."),
+			gettext_noop("Sets the planner's assumption about the size of the data cache."),
+			gettext_noop("That is, the size of the cache used for PostgreSQL data files. "
+						 "This is measured in disk pages, which are normally 8 kB each."),
 			GUC_UNIT_BLOCKS,
 		},
 		&effective_cache_size,