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-rw-r--r--doc/src/sgml/maintenance.sgml7
-rw-r--r--src/backend/access/transam/multixact.c2
2 files changed, 5 insertions, 4 deletions
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
index 8b2161da291..4383862981c 100644
--- a/doc/src/sgml/maintenance.sgml
+++ b/doc/src/sgml/maintenance.sgml
@@ -655,11 +655,12 @@ HINT: Stop the postmaster and use a standalone backend to VACUUM in "mydb".
<para>
As a safety device, a whole-table vacuum scan will occur for any table
whose multixact-age is greater than
- <xref linkend="guc-autovacuum-multixact-freeze-max-age">.
- This will occur even if autovacuum is nominally disabled. Whole-table
+ <xref linkend="guc-autovacuum-multixact-freeze-max-age">. Whole-table
vacuum scans will also occur progressively for all tables, starting with
those that have the oldest multixact-age, if the amount of used member
- storage space exceeds the amount 25% of the addressible storage space.
+ storage space exceeds the amount 50% of the addressible storage space.
+ Both of these kinds of whole-table scans will occur even if autovacuum is
+ nominally disabled.
</para>
</sect3>
</sect2>
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index f26f47e96b5..699497c4c3f 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -167,7 +167,7 @@
((xid) % MULTIXACT_MEMBERS_PER_MEMBERGROUP) * sizeof(TransactionId))
/* Multixact members wraparound thresholds. */
-#define MULTIXACT_MEMBER_SAFE_THRESHOLD (MaxMultiXactOffset / 4)
+#define MULTIXACT_MEMBER_SAFE_THRESHOLD (MaxMultiXactOffset / 2)
#define MULTIXACT_MEMBER_DANGER_THRESHOLD \
(MaxMultiXactOffset - MaxMultiXactOffset / 4)