Glossary - M

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The ability of an item, under stated conditions of use, to be retained in, or restored to, a state in which it can perform its required function, when maintenance is performed under stated conditions and using prescribed procedures and resources.

It should be noted that:

  • maintainability may, depending upon the particular analysis situation, be stated by one or several maintainability characteristics, such as probability distribution or mean active repair time
  • the value of the maintainability characteristic may differ for different maintenance situations
  • when the term 'maintainability' is used as a maintainability characteristic, it always denotes the intention that active maintenance is carried out within a given period of time.

From an asset planning and management perspective, when considering 'maintainability' characteristics, the following criteria should be noted:

  • serviceability -the ability of an item to be inspected and maintained under stated conditions and using prescribed procedures and resources
  • testability - the ability of an item to be easily and economically tested. Source S2 AS/NZS ISO 9000:2000.

A characteristic of design and installation, usually identified by the time and effort that will be required to retain an item as near as practical to its new or desired condition within a given period of time. Source: N1

Maintainability Index

A form of performance indicator such as the ratio of the required asset maintenance per annum as a percent of the capital replacement value compared with the norm for that type of asset. Source: G3


The combination of all technical and corresponding administrative actions carried out to restore an item to a state in which it can perform its required function.

Refer also to:

  • condition monitoring - the practice of making and assessing measurements of physical quantities on operating plant for the purpose of judging its fitness for continuing service. Source S2 : AS/NZS ISO 9000:2000
  • corrective maintenance- maintenance carried out after a failure has occurred in order to restore the item to a state in which it can perform its required function
  • preventative maintenance -maintenance carried out at predetermined intervals or other prescribed criteria, intended to reduce the probability of failure or degradation of performance of an item.
    All regular and routine actions necessary for retaining an item or asset in as near as practical to its original condition, but excluding rehabilitation. Refer also to Planned and Unplanned Maintenance. Source: G1
  • predictive maintenance - maintenance carried out based on the condition of the asset where attributes of the asset such as temperature, vibration, frequency, oil residuals and the like are used to ascertain the nature and the timing of the maintenance intervention.

Maintenance does not include modification of an asset from its original condition; therefore activity to sustain a building at its designed level of service is not considered to be maintenance if it involves modification of the asset from its original condition (or design). Source: G3

Maintenance Managed Item

The Maintenance Managed Item (MMI) level is that level for maintenance detail elected for the organization asset register. The MMI could be a whole building in some systems, whereas in more sophisticated systems it could be a shaft beading on an electric motor. Source: G3

Best Appropriate Practice requires that the level of detail in the asset register should allow for the recording of data down to the Maintenance Managed Item (MMI) level. Source: G1

"Maintenance Managed Item" or "MMI" refers to the lowest level of an asset's physical structure that is to be recognized within an asset register where the registry is structured as a nested hierarchy of physical assets. Typically, an MMI is set at that level of the hierarchy at which an asset is individually maintained or at which management decisions to repair, renew or replace are made.

Maintenance Management

The organization of maintenance activities within an agreed policy.

Maintenance Manual

Collated information and advice on the maintenance requirements of an item, or group of items in written and graphic form. Source: G1

Maintenance Planning

The process that provides a strategic link between an agency's maintenance program and its corporate directions and core business. Source: P1

Maintenance Policy

A formalized framework, accepted by senior management, within which decisions on maintenance are taken. Source: G3

Maintenance Priorities

A set of nominated maintenance activities ranked in order of priority based on given criteria (e.g. maintenance management policy, emergency work execution, etc). Source: G3

Maintenance Program

A specific plan of identified maintenance activities to be undertaken and recorded for an asset or aggregation of assets. Source: N1

Maintenance Reliability Characteristics

From a maintenance planning perspective the following reliability characteristics are important

  • mean life - the mean value of the length of the times to failure of all items in a population, under stated conditions
  • mean time to failure (MTTF) - in a stated period in the life of a population of items, the ratio of the cumulative time to the total number of failures in the population during the period, under stated conditions
  • mean time to repair (MTTR) - in a stated period in the life of a population of items, the ratio of the cumulative time to the total number of repairs in the population during the period, under stated conditions
  • mean time between failures (MTBF) - for a stated period in the life of an item, or a population of items, the mean value of the length of time between each item's consecutive failures, calculated as the ratio of the cumulative time to the total number of failures, under stated conditions
  • mean time to first failure (MTTFF) - the mean value of the times to the first failures of items in a population of items. Source S2 : AS/NZS ISO 8402:1994.

Maintenance Schedule

A formal plan that details the management process that will be implemented for a specific asset or group of assets from within the agency's asset portfolio. Source S2

Maintenance Service Criteria

Specified maintenance standards and levels of service for each asset, or appropriate aggregation of assets. Source: G1

Maintenance Standards

The standards set for the maintenance service such as preventive maintenance schedules, operation and maintenance manuals, codes of practice, estimating criteria, statutory regulations and mandatory requirements - in accordance with maintenance quality objectives and the asset standard classification. Source: G3

Management System

A system to establish policy and objectives and to achieve those objectives. It should be noted that the management system of an organization can include a range of sub-sets that collectively constitute the whole.

These sub-sets usually include the following

  • quality management system
  • human resource management system
  • fiscal management system
  • asset management system
  • information management system
  • environmental management system. Source S2 AS/NZS ISO 9000:2000.

Manager, Asset Management Services

A position within an organization that has the responsibility for the management of the Asset Management Services Team. The team's role is the implementation of the Corporation's Asset Management Improvement Plan. Source: G1

Market Value

The estimated amount for which an asset should exchange between a willing buyer and a willing seller in an arms length transaction, after proper marketing wherein the parties act knowledgeably, prudently and without compulsion. Source: I2

Maximum Mathematical Probability

The determination of the largest, most probable outcome, or the largest probability weighted outcome. Source: G3

Minimum Competency

From an asset management perspective, this term refers to the minimum human resource level of skill sets necessary to deliver the required service delivery outputs. Source: A7


Works undertaken to modify the characteristics or components of an asset so that its life is extended, it better delivers the required service, or it improves its safety. Source: G1

Modified Accrual

A basis of accounting, used exclusively in governmental accounting, according to which 1) revenues are recognized in the accounting period in which they become available and measurable and (2) expenditures are recognized in the accounting period in which the fund liability is incurred, if measurable, except for unmatured interest on general long-term debt and certain similar accrued obligations, which are recognized when due.


Periodic or continuous sampling to determine a previously defined level. This level could refer to an asset attaining a service delivery output performance target. It could also refer to the determination of pollution or radioactivity levels etc. In short, it refers to the periodic measuring or sampling some thing, to gain assurance that it has either attained a predetermined level, or conversely, that it has not exceeded a predetermined level. Source S2


The temporary decommissioning of assets to enable them to be stored and later reactivated. Source: G1

Multi-Stage Biding

The process of selecting a preferred service provider using a number of individual bid stages, such as short-listing or pre-qualification prior to the final bid. Source S2