Oracle’s option that neglects DR on SUN
I’m in no way an Oracle expert and my opinion has no influence but still I’d like to point out on a ridiculously stupid behavior caused by a hidden Oracle’s parameter called _enable_NUMA_optimization. As I’ve been told by our DBAs, in Oracle 9 this option was set to FALSE but in Oracle 10.2.0.1 they decided to change its default value to TRUE. Not a big deal. A metalink note pledges that setting this option to TRUE improves the performance by splitting SGA into multiple segments (ipcs -a confirms that) and as a result reduces the total number of remote cache misses on a large system. But in the real life it’s not as glaring as it sounds. Conversely, with this parameter set to TRUE don’t even think about adding/removing SBs/CMUs into your big and beefy Sun box.
Per Oracle development, adding/removing processor groups are not supported. Oracle does not support dynamic reconfiguration with instance up while running on Solaris 5.9 or 10 when NUMA is enabled.
Isn’t that sweat?!
P.S. If you have a Metalink account then check Doc ID: 761156.1 for more details.
P.P.S. Update. Oracle has published a new alert, Doc ID 759565.1, that discuss their current guidance on NUMA optimization. They now discourage setting hidden Oracle parameters in favor of applying a patch that disables Oracle NUMA optimizations by default on 10.2.04 and 11.1.0.7. This update was taken from here.