diff --git a/admin/tool/replace/index.php b/admin/tool/replace/index.php
index 11e1068576b..67d945ee427 100644
--- a/admin/tool/replace/index.php
+++ b/admin/tool/replace/index.php
@@ -49,6 +49,7 @@ if ($DB->get_dbfamily() !== 'mysql' and $DB->get_dbfamily() !== 'postgres') {
 
 if (!data_submitted() or !$search or !$replace or !confirm_sesskey() or !$sure) {   /// Print a form
     echo $OUTPUT->notification(get_string('notsupported', 'tool_replace'));
+    echo $OUTPUT->notification(get_string('excludedtables', 'tool_replace'));
 
     echo $OUTPUT->box_start();
     echo '<div class="mdl-align">';
diff --git a/admin/tool/replace/lang/en/tool_replace.php b/admin/tool/replace/lang/en/tool_replace.php
index 2193805f13e..9103e890ebc 100644
--- a/admin/tool/replace/lang/en/tool_replace.php
+++ b/admin/tool/replace/lang/en/tool_replace.php
@@ -24,6 +24,7 @@
  */
 
 $string['disclaimer'] = 'I understand the risks of this operation:';
+$string['excludedtables'] = 'Several tables are not updated as part of the text replacement. This include configuration, log, events, and session tables.';
 $string['pageheader'] = 'Search and replace text throughout the whole database';
 $string['notifyfinished'] = '...finished';
 $string['notifyrebuilding'] = 'Rebuilding course cache...';
@@ -33,4 +34,4 @@ $string['pluginname'] = 'DB search and replace';
 $string['replacewith'] = 'Replace with this string:';
 $string['replacewithhelp'] = 'usually new server URL';
 $string['searchwholedb'] = 'Search whole database for:';
-$string['searchwholedbhelp'] = 'usually previous server URL';
\ No newline at end of file
+$string['searchwholedbhelp'] = 'usually previous server URL';
diff --git a/lib/adminlib.php b/lib/adminlib.php
index fe4dc93a7c0..178244558bc 100644
--- a/lib/adminlib.php
+++ b/lib/adminlib.php
@@ -6668,7 +6668,7 @@ function db_replace($search, $replace) {
     global $DB, $CFG, $OUTPUT;
 
     // TODO: this is horrible hack, we should do whitelisting and each plugin should be responsible for proper replacing...
-    $skiptables = array('config', 'config_plugins', 'config_log', 'upgrade_log',
+    $skiptables = array('config', 'config_plugins', 'config_log', 'upgrade_log', 'log',
                         'filter_config', 'sessions', 'events_queue', 'repository_instance_config',
                         'block_instances', '');