Scaling DB2 Connect CPUs

In these tests, the number of CPUs defined for the DB2 Connect™ z/VM® guest was varied from one to two. The memory size was 1 GB. The think time value for the IRWW workload driver was varied from 2000 milliseconds to 5000 milliseconds and the number of user threads was held constant at 500. The z/VM LPAR was assigned six CPUs and the z/OS® LPAR was assigned four CPUs. The parameter, MAXAGENTS, was set high enough that the number of active connections was not limited.

Figure 1 shows throughput for DB2 Connect z/VM guests with one and two virtual CPUs and scaling think times from 2000 to 5000 milliseconds.

Figure 2 shows CPU utilization for DB2 Connect z/VM guests with one and two virtual CPUs and scaling think times from 2000 to 5000 milliseconds

Observations

There is a slight throughput advantage in the one CPU case for think times of 2000 milliseconds and 2500 milliseconds. At higher think times there is no difference in throughput. CPU utilization on the DB2 Connect server for the two CPU case is slightly higher than the one CPU case. The overall CPU load on the systems is very low (be aware that 100% means one CPU is fully utilized).

Conclusion

The IRWW workload throughput is not affected by the number of virtual CPUs. A single CPU for the DB2 Connect system would be sufficient for this type of workload. For a better comparison of the DB2 Connect behavior under these two very different workloads, we decided to use two CPUs on the DB2 Connect system for further runs.