Scaling DB2 Connect memory

In these tests, the DB2 Connect™ z/VM® guest used two virtual CPUs and 512 MB, 1 GB, and 2 GB of memory, depending on the run. The Trade 6 workload driver users were 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 when scaling DB2 Connect z/VM guest memory from 512 MB to 2 GB and Trade users from 400 to 600.

Observations

At 400 users, the throughput for the three memory configuration scenarios was almost identical. For the 1 GB and 2 GB memory scenarios, the throughput is also almost identical. Using more than 400 Trade users in the 512 MB scenario causes significant swapping on Linux®.

Conclusion

We did not exceed 400 users at 512 MB of main memory on the DB2 Connect system. Although a relatively small amount of swapping occurs at 400 users, swapping increases above 400 users so we did not want go above that number of users.

It is recommended that if MAXAGENTS is set to 400 or greater, DB2 Connect should be run with 1 GB of memory for active connections when running applications similar to Trade 6. There is nearly no advantage to 2 GB of main memory for our test scenarios. Therefore, we used 1 GB of main memory on the DB2 Connect system for all further runs.