Oldest xmin is far in the past

Hi,

Coming back from vacation, I find a PostgreSQL database cluster (Pg
version: 9.0.4)
with 5 databases, which for the past 5 days have logged these messages:

WARNING: oldest xmin is far in the past
HINT: Close open transactions soon to avoid wraparound problems.

The cluster has been running continously for over 9 months with autovacuum
enabled.

Doing a:

vacuumdb -h <host> -U postgres -v -a

vacuums the tables, and also emits the same messages while vacuuming:

WARNING: oldest xmin is far in the past
HINT: Close open transactions soon to avoid wraparound problems.

Checking with:

"SELECT datname, age(datfrozenxid) FROM pg_database;"

vacuum did not reduce the age of datfrozenxid:

datname | age
------------+-----------
template1 | 208249541
template0 | 208249541
postgres | 208249541
db1 | 208249541
db2 | 208249541
db3 | 208249541
db4 | 208249541
db5 | 208249541

Running

"SELECT relname, age(relfrozenxid) FROM pg_class WHERE relkind = 'r' order
by age(relfrozenxid) desc;"

on each database, I see that the age is still high for some of the shared
catalogs:

**pg_class:
relname | age
-------------------------+-----------
pg_db_role_setting | 208249542
pg_authid | 208249542
pg_database | 208249542
pg_shdescription | 208249542
pg_shdepend | 208249542
pg_auth_members | 208249542
pg_pltemplate | 208249542
pg_tablespace | 208249542

Max age of usergenerated tables (ie not pg_ tables):

max age(relfrozenxid)
db1: 169036643
db2: 208249548
db3: 169036553
db4: 191294331
db5: 64496585

Looking at 'db2' in the cluster, I see that in fact _every relation_ listed
with:

"SELECT relname, age(relfrozenxid) FROM pg_class WHERE relkind = 'r'
order by age(relfrozenxid) desc;"

have

age(relfrozenxid) = 208249548 (at the time of running the query)

Could the problem be in this 'db2' ?

However running 'vacuumdb -h <host> -U postgres -a' does not seem to fix
the problem.

Using:

"select procpid, datname,usename,query_start from pg_stat_activity order
by query_start;"

I cannot find any 'idle in transaction' connected, and I can see one 'idle'
connection
(but not 'idle in transaction') which is almost 24 hours old, the rest is
from early this morning.

Also:

ps auxww|grep 'trans'

finds no 'idle in transactions'.

So, I'm looking for ways to fix this 'wraparound' problem for this database
cluster.

Are any of these options candidates for solving the wraparound issue ?

OPTION 1) Shutdown all application brokers connected to the databases and
then do another

vacuumdb -h <host> -U postgres -v -a

OPTION 2) Shutdown all application brokers connected, stop the database
cluster, start the database cluster
and then do another

vacuumdb -h <host> -U postgres -v -a

OPTION 3) Close all brokers connected to the database,
do a full dump of db2 (which has user tables with highest xid age),
drop database db2
restore db2

OPTION 4) Close all brokers connected to the database,
do a full dump of all 5 databases,
rename the the datadb cluster dir: mv /dbcluster /dbcluster.old
do a new initdb /dbcluster
restore the 5 databases to new /dbcluster

Or are there anything else I could try to fix this ?

Thank you

Christian