On 08/07/2016 10:26 AM, Philippe Girolami wrote:
I am seeing something weird though (again, this is v9.1): after my database
became usable again, I started getting the 10M warning on template0. So I made
it connectable and ran VACUUM
FREEZE on it and made it unconnectable again. That resolve the warning.
However, I see the “age” keeps increasing on that database as I ran queries on
my own db. Yesterday the age was 32 and now it’s already 77933902
Just to be sure you are talking about template0?
Yes, I am
Is that to be expected ? I didn’t expect it
As I understand it;
1) xid's are global to the cluster.
2) age(xid) measures the difference between the latest global xid to
whatever xid you supply it.
3) age(datfrozenxid) measures the difference between the minimum value
for the table frozen ids in a particular database and the latest global xid.
4) template0 has a datfrozenxid so there is something for age(xid) to
compute, it just does not mean anything as long as template0 is really a
read-only database. In other words template0 is not actually
contributing any transactions to the consumption of the global store of
xids.
Yes, I understand. I’m just worried that if I see the WARNING for the 100M
mark, I’m afraid when it gets to the 1M mark on that database it will shut down
the cluster.
More weirdness this afternoon : the wraparound ERROR showed up again even
though I have trouble believing I burned through so many transactions in under
a day. But let’s assume I did, here is what I noticed
1) I vacuumed all other databases. For everyone of those, the age went down to
50M instead of zero. Is that normal ?
2) The only database that didn’t work on was template0 (the age did not
change). It did work on template1
That is expected as template0 is read-only and so VACUUM will not work
on it.
Should I suspect something fishy going on ?
Not sure without more information.
1) Can you be specific about your database references? 'That database'
is open-ended.
2) Show the actual numbers from your xid queries. Both the raw values
and the age() transformed ones.
3) What are your configuration parameters for the variables mentioned in
the section below?:
https://www.postgresql.org/docs/9.1/static/routine-vacuuming.html#VACUUM-FOR-WRAPAROUND
4) If you want to get an idea of fast xid's are being created a quick
and dirty way is from here:
https://www.postgresql.org/docs/9.1/static/functions-info.html
txid_current() bigint get current transaction ID
Now if you do select txid_current() outside a transaction it will create
an xid on its own, still if you repeat it over some interval of time you
will get an idea of how fast the server is going through xid's.
Thanks
--
Adrian Klaver
adrian.kla...@aklaver.com
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