Sysplex distributor enhanced workload distribution for z/OS multi-tier, OPTLOCAL configurations

In environments in which OPTLOCAL is used to optimize the load balancing between tier 1 and tier 2 server applications, more optimization is possible if sysplex distributor is also used as the load balancer for the tier 1 server applications. This optimization makes both tiers of z/OS® server applications on a given system visible to sysplex distributor when making a load balancing decision on an incoming tier 1 connection request. When you are using WLM-based recommendations such as SERVERWLM, this optimization enables sysplex distributor to compute a composite WLM weight for each system, which includes the capacity, performance, and health characteristics of both the tier 1 server applications and the tier 2 server applications. Figure 1 shows an example configuration that enables this enhancement.

Figure 1. Enhanced z/OS multi-tier application load balancing using sysplex distributor

Shows two-tier server applications that are optimized by using enhanced workload distribution of sysplex distributor

As shown in Figure 1, two VIPADISTRIBUTE statements are required in this configuration. The first statement for DVIPA1 represents the distribution to the tier 1 server applications, a cluster of WebSphere® Application Server instances running on each LPAR. The second statement for DVIPA2 represents the tier 2 server applications, a cluster of CICS® regions on the same LPARs as the tier 1 servers.

The VIPADISTRIBUTE statement for each DVIPA includes a tier specification that indicates the role of each DVIPA (TIER1 or TIER2). The two DVIPAs are linked by a common group name specification, WASCICS. This association enables sysplex distributor to compute a single weight for each DVIPA1 target system that reflects the combination weight of the tier 1 and tier 2 server applications that are running on that system. Sysplex distributor performs its workload balancing of incoming connection requests to DVIPA1 based on these combined weights, enabling distribution of requests to the target z/OS systems to be based on the aggregate capacity of each system to perform the processing of both server application tiers.

In addition, because the VIPADISTRIBUTE statement for DVIPA2 also includes the OPTLOCAL specification, incoming tier 1 connection requests are typically directed to a system that also enables the subsequent tier 2 connection requests to stay local. This provides an improvement over the base OPTLOCAL configuration, because new workload is directed toward systems that have more capacity to process the work while retaining the local optimizations provided by OPTLOCAL.

Rule: To use this feature, the distribution method for the tier 1 and tier 2 servers must be BASEWLM or SERVERWLM.

Guideline: To take full advantage of this feature, set the distribution method for both tier 1 and tier 2 servers to SERVERWLM. This enables sysplex distributor to obtain server-specific WLM recommendations for each application server tier; the combined weight reflects the composite performance of the servers instead of the capacity of the system.

For more information about the TIER1 and TIER2 keywords on the VIPADISTRIBUTE statement in the VIPADYNAMIC block, see z/OS Communications Server: IP Configuration Reference.