Scaling DB2 Connect virtual CPUs

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In these tests, one or two virtual CPUs were defined for the DB2 Connect z/VM® guest and 1 GB of memory was used. The number of Trade 6 users was scaled from 50 to 600. The z/VM LPAR was assigned five CPUs and the z/OS® LPAR was assigned six 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, scaling Trade users from 400 to 600.

Figure 1. Trade 6 workload - CPU scaling throughput
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Figure 2 shows CPU utilization for DB2 Connect z/VM guests with one and two virtual CPUs when the Trade users were scaled from 400 - 600.

Figure 2. Trade 6 CPU scaling
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Observations

With our workload, a DB2 Connect server with one virtual CPU was fully utilized quickly, which limited the throughput. Throughput in the one CPU scenario reaches its peak at 400 users and decreases beyond that. When DB2 Connect has more than one CPU, throughput improves over the one CPU case by a factor of 1.35 with 600 users.

Conclusion

DB2 Connect with a single virtual CPU is mostly overloaded with this high number of users and this workload. It works more effectively in a multi-CPU environment. It is recommended that DB2 Connect be run with a minimum of two virtual CPUs to achieve additional throughput.