after i backdb->dropdb->restoredb and then vacuum analy+full -> vacuum freeze the XID had been increased by 4 billion in two weeks...is it noraml? what's the definetion of XID? " select * from mybook" SQL command also increase the XID ? reference: http://www.postgresql.org/docs/9.0/static/routine-vacuuming.html -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance