DB2 for Linux, UNIX, and Windows Version 9.7 provides the option of tightly integrating DB2 workload management capabilities with the workload management capabilities provided by the AIX® or Linux operating systems. Specifically, you have the option of integrating DB2 service classes with the equivalent concept in AIX Workload Manager (AIX WLM) and Linux workload management (Linux WLM) in order to take advantage of the native control and monitoring capabilities that these products provide.
The provision of an external tag, or outbound correlator, as part of a DB2 service class definition enables the DB2 database manager to interact with the workload management interfaces provided as part of the operating system (OS) and to automatically associate each DB2 agent, which is an operating system thread, with a specific operating system workload management (OS WLM) entity. After this task is done, then the rules and limits defined for that OS WLM entity are then imposed on the DB2 agent by the OS.
As a general rule, OS WLM products provide two types of controls: hard and soft. Hard controls specify a value or allocation of a specific resource which is invariant regardless of the degree of utilization of that resource. Soft controls specify a value or allocation of a specific resource which is enforced only when the resource is highly used, otherwise they are not enforced.
AIX WLM supports the definition of a service superclass or service subclass in a two level, parent-child relationship similar to that provided by DB2 service superclasses and subclasses. AIX WLM provides for the control of CPU resource at the AIX WLM service class level in various forms, including soft and hard settings.
Linux WLM supports the definition of control groups, or cgroups, through which the administrator can control resource consumption. Cgroups can be defined in an unlimited parent-child hierarchical structure to each other which exceeds the two level structure provided by DB2 service superclasses and subclasses. Linux WLM provides for the control of CPU resource at the cgroup level through a soft setting.
The typical use of OS WLM integration seen to date in customer implementations is to supplement the native controls within DB2 for Linux, UNIX, and Windows, such as concurrency thresholds, to better protect high priority work from the resource demands of lower priority work. Protecting high priority work is done by capping the CPU resource available to the low priority work. The vast majority of these implementations used AIX WLM hard controls, with a smaller subset using soft controls when the system is highly utilized.