Peter Eisentraut <peter_e@gmx.net> writes:
> Is it safe to read pg_control externally without a lock? pg_controldata
> will just report a CRC error and proceed, and if you're not sure you can
> just run it again. But if a promotion fails every so often because of
> concurrent pg_control writes, that would make this feature annoying.
Just retry the read till you don't get a CRC error.
regards, tom lane