Hi, we are building a 9.3 instance on CentOS with 32 GB of RAM. What is the recommended value for SHMMAX the documentation was far less is needed but not exactly how much. We used 25% of total memory < 9.3. But what should we use now ? 5% of total memory or just 10 MB or 10 KB ? Do we even need to mess with sysctl.conf? The documentation table 17-1 shows just 1 kb is needed yet below under linux the example uses 17 GB of SHMMAX. We will run several instances on one server.
At 9.3 the mechanism for shared memory allocation has changed. Now it uses mmap(). And so, there is no more need to adjust the SHMMAX parameter (at least not more than the 1KB).
So the answer to your question is basically that you don't need to mess sysctl.conf anymore to change SHMMAX (at least not in CentOS). You still may need to tweak there to change semaphores limits.
Best regards,
-- Matheus de Oliveira Analista de Banco de Dados Dextra Sistemas - MPS.Br nível F! www.dextra.com.br/postgres