On Wednesday, February 14, 2018, pavan95 <pavan.postgres...@gmail.com>
> Hi all,
> Is it possible to upgrade an existing postgresql 9.1 production system to
> latest Postgres 10.0 version?
> The main requirement is to get rid of downtime. Please help me out!
Zero downtime is only possible by standing up a hot-standby then failing
over to it. Same-server upgrade you can do via pg_upgrade but it does
involve downtime. There are lots of material and options online, including
the docs, for setting up hot-standby replication.