diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml
index da431f8369..8b251f9e5d 100644
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -568,10 +568,17 @@ ALTER TABLE [ IF EXISTS ] name
That can be done with VACUUM
FULL>, or one of the forms
of ALTER TABLE> that forces a table rewrite.
+ For planner related parameters, changes will take effect from the next
+ time the table is locked so currently executing queries will not be
+ affected.
- Changing fillfactor and autovacuum storage parameters acquires a SHARE UPDATE EXCLUSIVE lock.
+ SHARE UPDATE EXCLUSIVE lock will be taken for
+ fillfactor and autovacuum storage parameters, as well as the
+ following planner related parameters:
+ effective_io_concurrency, parallel_workers, seq_page_cost
+ random_page_cost, n_distinct and n_distinct_inherited.