Class priority in Workload Manager

WLM allocates resources to classes by giving a priority to each class for each resource.

The priority of a class is dynamic and is based on the tier, shares, limits, and the current consumption of the class. At any given time, the highest priority class or classes will be given preferential access to resources. At the highest level, tiers represent non-overlapping ranges of class priority. Classes in tier 0 will always be guaranteed to have a higher priority than classes in tier 1 (unless over hard maximum).

When determining class priority, WLM enforces its constraints with the following precedence (highest to lowest):

hard limits: If class consumption exceeds the hard maximum for a resource, the class is given the lowest-possible priority for the resource and will be denied access until its consumption falls below this limit.
tier: In the absence of hard limits, a class's priority will be bounded by the minimum and maximum allowed priority for its tier.
soft limits: If class consumption is below the minimum of the soft maximum limits for a resource, the class is given the highest-priority in the tier. If class consumption is above the soft maximum, the class is given the lowest-priority in the tier.
shares: These are used to calculated the class consumption targets for each resource. The class priority is increased as class consumption falls below the target, and is decreased as it rises above the target. Note that soft limits have higher precedence and the class's priority will be determined based on them, when applicable.

Even though both shares and limits can be used for each class and for each resource, results are more predictable if only one or the other is used per class.