diff --git a/admin/index.php b/admin/index.php
index <HASH>..<HASH> 100644
--- a/admin/index.php
+++ b/admin/index.php
@@ -52,6 +52,13 @@
         error("The PHP server variable 'file_uploads' is not turned On - $documentationlink");
     }
 
+    if (empty($CFG->prefix) && $CFG->dbtype != 'mysql') {  //Enforce prefixes for everybody but mysql
+        error('$CFG->prefix can\'t be empty for your target DB (' . $CFG->dbtype . ')');
+    }
+
+    if ($CFG->dbtype == 'oci8po' && strlen($CFG->prefix) > 2) { //Max prefix length for Oracle is 2cc
+        error('$CFG->prefix maximum allowed length for Oracle DBs is 2cc.');
+    }
 
 /// Check that config.php has been edited
Now admin/index.php checks for proper prefixes (MDL-<I>)

Merged from MOODLE_<I>_STABLE