Re: shared_buffers vs. -B flag: 7.4

elein@varlena.com (elein) writes:
> However, if you use the -B option on the pg_ctl
> start up, postgres starts up fine.  And
> the shared_buffers value shown by show
> is the higher value.

It behaves as expected for me, in both 7.4 and CVS tip.  Are you sure
your test case wasn't such that the higher -B value in fact worked?
(For instance, maybe you stopped another postmaster that was using some
of the shmem.)

$ postmaster -B 65000
FATAL:  could not create shared memory segment: Not enough space
DETAIL:  Failed system call was shmget(key=5474001, size=543997952, 03600).
HINT:  This error usually means that PostgreSQL's request for a shared memory segment exceeded available memory or swap
space.To reduce the request size (currently 543997952 bytes), reduce PostgreSQL's shared_buffers parameter (currently
65000)and/or its max_connections parameter (currently 100). 
        The PostgreSQL documentation contains more information about shared memory configuration.
$

            regards, tom lane