diff --git a/core/includes/database.inc b/core/includes/database.inc
index 0197377..3327c19 100644
--- a/core/includes/database.inc
+++ b/core/includes/database.inc
@@ -359,6 +359,13 @@ function db_delete($table, array $options = array()) {
 /**
  * Returns a new TruncateQuery object for the active database.
  *
+ * Warning: Truncating a database table may cause it to be unavailable for
+ * reading and/or writing for a period. Truncation of large tables may
+ * result in a longer unavailability for other requests. Consider using other
+ * data structures and a scoped deletion/merge rather than this function to
+ * experience less locking. The exact impact will vary per database driver
+ * type and version.
+ *
  * @param $table
  *   The table from which to delete.
  * @param $options