From Wikipedia, the free encyclopedia
Jump to: navigation, search
          This article is of interest to the following WikiProjects:
WikiProject Systems  
WikiProject icon This article is within the scope of WikiProject Systems, which collaborates on articles related to systems and systems science.
 ???  This article has not yet received a rating on the project's quality scale.
 ???  This article has not yet received a rating on the project's importance scale.
Taskforce icon
This article is not associated with a particular field. Fields are listed on the template page.
WikiProject Engineering  
WikiProject icon This article is within the scope of WikiProject Engineering, a collaborative effort to improve the coverage of engineering on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
 ???  This article has not yet received a rating on the project's quality scale.
 ???  This article has not yet received a rating on the project's importance scale.


Some content has been moved to Forty-nine charismatic virtues. Peter Manchester 13:15, 25 Nov 2003 (UTC)

I'm trying to find a definition of Availability that can be sensibly used in a legal document relating to a web site hosting service. The current definition on Wikipedia doen't seem to fulfil this requirement. I'm sure there is a service-related definition of Availability in ITIL somewhere, but I haven't yet found it. Can anybody help with this? penis

heyyy what up —Preceding unsigned comment added by (talk) 23:12, 27 January 2010 (UTC)

Dubious definition[edit]

The article states the following:

Limiting (or steady-state) availability is represented by[citation needed]

    A = \lim_{t \rightarrow \infty} A(t).

Limiting average availability is also defined on an interval (0,c] as,

    A_{\infty}=\lim_{c \rightarrow \infty} A_c = \lim_{c \rightarrow \infty}\frac{1}{c}\int_0^c A(t)\,dt,\quad c > 0.

I don't see how this can be accurate, however. The steady-state availability definition as stated doesn't look like it would converge. This appears to be more of an "instantaneous" availability that is evaluated as t gets large, which seems like a dubious procedure to me. I suspect a definition like:

    A = \lim_{c \rightarrow \infty} A_c.

is probably more accurate for steady-state (limiting) availability. (talk) 02:22, 23 August 2010 (UTC)

Inherent and Operational Availability[edit]

I read earlier today on Talk:Mean down time:

From Jones, Logistics Support Analysis Handbook (TAB Books inc.), the time clock for MTTR starts and ends only with the corrective maintenance cycle (fault detection, isolation through checkout). MDT accounts for all including delays where spares, support personnel or tools are not immediately available. MTTR is used in calculating Ai (Inherent Availability) where MDT is used in calculating Ao (Operational Availability).

This is good info, I'd like to include it, but I'm not sure what the best way to do that is. At a minimum, I believe the article needs to mention inherent availability and operational availability. (talk) 02:30, 23 August 2010 (UTC)

Mission Capable Rate[edit]

The military's notion of mission capable rate is a special case of system availability, so I've linked a number of pages that mention this term to this page. We should probably redirect mission capable rate to this page also. (talk) 00:31, 19 September 2010 (UTC)

Sounds swell. I've created the redirect. bahamut0013wordsdeeds 02:53, 19 September 2010 (UTC)

Available isn't available ?[edit]

The current definition seems MIL-STD based, should there be mention of alternative views?

For example in Semiconductor Equipment and Materials International SEMI-E10 specification or Reliability, Availability, and Maintainability, see -- see paper on Measuring Supercomputer RAS. I've also seen Availability and the different ways to calculate it

The alternative seems looking from a viewpoint of post-fact reporting on actual production measurements rather than a calculated KPP. I'm also thinking the military KPP usage has availability measured against time supposed to be up -- so 'scheduled downtime' does not count - and the SEMI usage has any downtime counted as downtime, and then focuses on how much uptime went to engineering tasks, idle time, and how much of actual runtime is in restart and rework time.

Anyone have viewpoint on including other measures in the article ? Markbassett (talk) 20:56, 30 July 2015 (UTC)