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UMA Measurement Layer Interface (MLI)
Copyright © 1997 The Open Group

UMA Reference Model

The UMA reference model defines four layers and two interfaces, as shown in UMA Layers and Interfaces .

Figure: UMA Layers and Interfaces

Functional Layers

In order, from data capture to application program, the functional layers are:


UMA establishes two programmatic interfaces which concern data provider developers and measurement applications:

The interface between the DSL and the MCL is not formally specified. These two layers, though functionally distinct, may be combined in some implementations.

Components and Interfaces of UMA illustrates the two programmatic interfaces (DCI and MLI) in relation to the functionality of UMA components.

Figure: Components and Interfaces of UMA

UMA Characteristics

The three layers, DCL, MCL, and DSL, and the two interfaces, DCI and MLI, comprise the basic UMA facility. When this document describes UMA or refers to UMA characteristics, it is describing the combined capabilities of these layers and interfaces. The MLI isolates a MAP from the implementation details of the rest of UMA. Interactions between a MAP and UMA are carried out through the MLI.

The UMA reference model provides several advantages over the older data collection and display programs such as sar. The structure of the DCL, and the DCI, permits the extension of data collection to new devices or services without affecting existing programs.

Additionally, the architecture of the DCL allows the data from multiple providers to be collected by a single layer and this in turn improves the synchronisation of the collected data. For example, since the data reported by sar and various other statistical commands use different data collection routines, there is an unpredictable time delay between datapoints collected by one program and datapoints collected by the other. With UMA, the collection is more closely synchronised.

By having UMA manage the collection and distribution of data, multiple application programs can use the same collected data. This results in savings of memory, disk space, and system overhead. The MLI and the DSL allow transparent communication across networks, therefore a MAP running on one system can manage and display data from another system across the network.

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