Entity relationships

Relationships are directed connections between two entities. Each relationship connects a parent entity and a child entity. 

For more information, see the following sections:

• Console workspace tree: The hierarchical tree in the TrueSight Capacity Optimization console workspace user interface is used to organize entities into groups and sub-groups for ease of administration. The tree is built using parent-child relationships. See Hierarchies for how hierarchies are used.

• Derived systems: A derived system can be used to represent calculated metric values from other systems. For example, a logical cluster (active/active or active/passive) can be defined as a derived system that is parent of the two cluster nodes. In this example, the CPU utilization of the derived cluster system is automatically calculated based on the CPU utilization of the nodes. See Deriving a new entity from existing resources.

• Reporting and data extraction: A report, view, or external data client can use relationships to extract related entities from TrueSight Capacity Optimization. For example, a client can extract all of the systems that support a service. See Creating custom reports.

Relationships can be made between any two entities in TrueSight Capacity Optimization, subject to these rules:

• A domain can be a parent of a system, or of a business driver, or of another domain.
• A system can be a parent of another system.
• A business driver can be a parent of another business driver.

The console workspace tree shows all of the visible relationships that are currently valid. If an entity is a child of two different entities, then the child is shown twice in the tree, once under each of its parents.

Relationship instances and validity periods

Relationships in TrueSight Capacity Optimization are represented in a manner similar to configuration metric instances, except that relationships are not about an entity, but about two entities at once.

Mathematically, a relationship instance of one type is defined between any two entities, during any time period in which both entities are known to TrueSight Capacity Optimization (that is, not dismissed). The instance may either be valid throughout that period, or not valid for any instant during that period, or valid for some sub-periods and invalid for the others. This is analogous to how configuration metric instances are valid or invalid through the life of an entity; see Metrics in TrueSight Capacity Optimization.

To represent these relationship instances, the TrueSight Capacity Optimization database contains for each instance a series of variable-length, non-overlapping validity periods, each representing a time period during which the relationship is valid. Because the validity periods in the series are non-overlapping, therefore at any given instant in time, the relationship instance is either valid or not, never both.

A TrueSight Capacity Optimization database may contain thousands of entities that are alive (not dismissed) at the same time. Theoretically, there is an instance of a relationship of each type between each pair of these entities. But because most entities are related to only a few others in practice, most of these relationship instances are not valid at any time, and do not need to be explicitly represented in the TrueSight Capacity Optimization database. The database stores only those relationships that are valid at least during a single period.

The definition of relationships has a schema that appears as a set of additional columns in the Dataset 59 (OBJREL). The most important aspects of relationships are:

Of the above aspects of a relationship, the first two (Type and Entity pair) uniquely identify the relationship instance. The other aspects add information about the instance.

Updating relationship instances

The various manual and automated operations on hierarchies described in Hierarchies seem simple. But the hierarchies visible in the console workspace tree represent only the current snapshot of the relationship graph in TrueSight Capacity Optimization. The relationship instances recorded in TrueSight Capacity Optimization represent parent-child connections over the entire time period from the creation of both entities to "infinity", an indeterminate future date.

For example, what seems like a move of an entity from one domain to another, as described in Adding system and business driver entities to a domain, is in fact a combination of two modifications:

• Marking the old relationship as valid through yesterday.

• Marking the new relationship as valid from today to infinity.

Thus, as long as both parent and child entities remain alive in TrueSight Capacity Optimization, it is possible to find out whether their parent-child relationship was valid or invalid at any time in the past.

When either or both of the entities is dismissed, however, the validity records of their relationships are automatically discarded.