Sybase IQ 12.6 Tuning for UltraSPARC T1 Platforms
Sybase IQ has a tuning parameter called -iqnumbercpus. It defaults to the number of CPU's on the server. For an 8-core T1000/T2000 platform
(which supports 4 threads per core - totaling 32 threads), that means it defaults to 32.
Testing has shown that values this high can cause certain types of queries to perform sub-optimally, resulting in very poor execution times.
The symptoms of this are a handful of threads using 100% of a hardware strand (user time, as observed via 'prstat -mL') for long periods of time.
This issue can be resolved by specifying a -iqnumbercpus parameter to something less than the default.
For example, a parallel, complex table insert that took over 6 hours with the default parameter dropped to 40 minutes by setting -iqnumbercpus to
8. Note that setting this to 8 does not limit Sybase IQ from using more than 8 CPU's (hardware strands), so you'll still benefit from the 32 strands.
It's application dependent on what the optimal value for -iqnumbercpus is. Consider starting with this parameter set to the number of strands/2.
