On Thu, 2020-05-07 at 13:33 -0700, Tory M Blue wrote:
> I hadn't noticed this until today, but a running 9.5 system with buffers at 10GB starts
> and has been running years without issues. (15GB available)
>
> Postgres 12 will not start with that configuration, complaining about memory availability.
> So Postgres12 won't start until shared buffers is 6GB, but even with that, my DB servers ,
> postgres queries started complaining about being unable to allocate memory "unable to allocate".
>
> So dropping them to 4GB (on a 15GB system), may help, but did I miss a huge note about
> significant memory changes between 9.5 to 12?
>
> Is there something else I'm missing that on busy systems is important, something introduced
> in 10 or 11 as again I'm not seeing anything noted in 12.
There must be something else running on the machine that allocates memory.
Did you perchance run the 9.5 and the v12 server on the same machine?
Yours,
Laurenz Albe
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