Configuring zIIP capacity for Db2 workloads

You must ensure that sufficient IBM® z Integrated Information Processor (zIIP) capacity is available to the LPAR where Db2 runs to maximize zIIPoffload, and support latency requirements.

Before you begin

See the information about planning for, configuring, and using zIIP engines in Using System z Integrated Information Processor (zIIP).

About this task

Some Db2 zIIP-eligible workloads, such as CPU parallel queries, utility operations, or low priority DRDA transactions might be able to tolerate increases in latency due to dispatching delays. However, system agents that execute under the system services address space (ssnmMSTR) and database services address space (ssnmDBM1) cannot tolerate significant CPU delay.

The system agents provide the subsystem level services such as prefetch and deferred write I/Os, castout, and log write I/Os and tend to perform very small units of work but can create bursts of zIIP-eligible work. Db2 can have upwards of 2,000 zIIP-eligible system agents running concurrently to service various Db2 activities. The tasks performed by system agents are not CPU intensive but dispatching delays can negatively impact workload throughput.


To protect latency-critical Db2 subsystems and workloads, such as Db2 system agents and business critical DRDA transactions and REST services, consider the following actions:

  1. Ensure that sufficient zIIP weight is defined for LPARs where Db2 for z/OS® workloads run.
    To ensure a physical zIIP engine is available to be dispatched on-demand for critical Db2 tasks with stringent latency requirements it is important to set the PR/SM weight and logical engine assignment so the LPAR has least one Vertical High logical zIIP engine assigned.
  2. Use simultaneous multi-threading in the z/OS LPAR on z13 or later processors to increase zIIP capacity when only one zIIP engine can be dedicated to the LPAR.
    The MT_ZIIP_MODE parameter in IEAOPTxx in SYS1.PARMLIB enables simultaneous multi-threading for zIIP engines and can result in overall zIIP capacity improvement.