When upgrading from pre 10.2.0.4 to 10.2.0.4, Oracle enables NUMA support. This has the effect that there can be multiple shared memory segments (MetaLink Note: 429872.1) although shmmax/shmall are set to high values.

I have read MetaLink Notes (7171446.8, 6730567.8, 6689903.8) and this blog entry, where a customer had problems on HP-UX with the default NUMA settings.

Better than that, it can also lead to instance crashes in 10.2.0.4 as reported in MetaLink Note 743191.1. Good news is that there is a patch available for Linux x86_64/10.2.0.4.

I have asked Oracle Support whether it is safe to leave NUMA enabled for Linux Itanium, but they would not comment on it. Instead they asked me to check with the OS vendor. Great. ;-(