With workload management (WLM), we can control the number of servants that are running and how they are performing. WLM manages the response time and throughput of transactions according to their assigned service class, the associated performance objectives, and the availability of system resources. To meet these goals, WLM sometimes needs to control or override the number of servants that are active.
Product applications are deployed within a generic server. One or more server instances must be defined on one or more systems within a node. Each server instance consists of a controller and one or more servants. The controllers are started by MVS™ as started tasks, and servants are started by WLM, as they are needed.
WLM dynamic application environments can be enabled on the z/OS system if you are running on z/OS Release 2, with the service update for APAR OW54622 installed, or if you are running on a higher level of z/OS. If we have WLM dynamic application environments enabled on the system, WLM honors the specifications for the number of servants. If we are using static application environments, which is a setting specified through the WLM ISPF panels, then you must also enable multiple servants by indicating No limit in the WLM ISPF panels.
Avoid trouble: If we use multiple servants, remember that:
- The console and the deployment manager no longer have serialization requirements that only work in a single JVM. Therefore, we can run these applications in a server with multiple servants.
- If we specify a maximum number of instances, workload management (WLM) cannot start more than the specified number of servants for this server instance.
- The maximum number of servants should be at least as large as the number of different service classes that might be used by transactions that are run in the server. The number must also account for the default CB-type service class and enclaves that might originate outside of the product servers and are classified by other classification rules, such as the IBM HTTP Server (IHS).
Controlling the minimum and maximum number of servants Use transaction classes to classify workload for WLM