Re: Should a DB vacuum use up a lot of space ? - Mailing list pgsql-general

From Philippe Girolami
Subject Re: Should a DB vacuum use up a lot of space ?
Date
Msg-id A7F092C1-1977-4D8E-91CC-3D97FC1928B4@mosaik.com
Whole thread Raw
In response to Re: Should a DB vacuum use up a lot of space ?  (Adrian Klaver <adrian.klaver@aklaver.com>)
Responses Re: Should a DB vacuum use up a lot of space ?  (John R Pierce <pierce@hogranch.com>)
Re: Should a DB vacuum use up a lot of space ?  (Adrian Klaver <adrian.klaver@aklaver.com>)
List pgsql-general
>> I am seeing something weird though (again, this is v9.1): after my database became usable again, I started getting
the10M 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
andnow 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
onthat 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
throughso 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

Should I suspect something fishy going on ?


Thanks



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