Elliot Chance <elliotcha...@gmail.com> writes:
> This is a hypothetical problem but not an impossible situation. Just curious
> about what would happen.
> Lets say you have an OLTP server that keeps very busy on a large database. In
> this large database you have one or more tables on super fast storage like a
> fusion IO card which is handling (for the sake of argument) 1 million
> transactions per second.
> Even though only one or a few tables are using almost all of the IO, pg_dump
> has to export a consistent snapshot of all the tables to somewhere else every
> 24 hours. But because it's such a large dataset (or perhaps just network
> congestion) the daily backup takes 2 hours.
> Heres the question, during that 2 hours more than 4 billion transactions
> could of occurred - so what's going to happen to your backup and/or database?
The DB will shut down to prevent wraparound once it gets 2 billion XIDs
in front of the oldest open snaphot.
regards, tom lane
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