Pending Maintenance Events With ForcedMaintenanceList

[Jürgen Strohhecker]

Dear all,

I have difficulties with the downtime entity object used to model regular maintenance of resource units. In the extended downtime entity example model attached, two machines are modelled as resource units that should be maintained for a duration of 5 s and a interval of 30 s. Everything seems to work fine if the entity delay "produce" duration is set to values smaller than 1 s. Values above result in an increasing number of pending maintenance events that never get executed. I would love to see a different maintenance behavior, that is, the machine should be forced into a shutdown for 5 s under any circumstance. I am sure that I make a simple mistake, but I do not see a way forward. Therefore, I would highly appreciate any suggestions.

Thank you very much

Jürgen

[Harry King]

Jürgen,

What you are asking for are 'ImmediateBreakdown' and 'ImmediateMaintenance' inputs for ResourceUnit. Unfortunately, it is not obvious how these features should work for resources. If the ResourceUnit seized by a SimEntity breaks down, should the SimEntity immediately stop whatever activity it is doing at the time? This would have to be implemented specially for every type of object that can receive a SimEntity, some of which do not implement breakdowns/maintenance themselves, such as EntityDelay and Queue.

The first problem you described is much easier to solve. Both ResourceUnits ('Machine1' and 'Machine2') use the same DowntimeEntity ('Maintenance') as the input to their ForcedMaintenanceList input. Since these are 'forced' maintenance activities, it is necessary for BOTH Machine1 and Machine2 to be idle before the downtime event can begin. This is a requirement because both machines must be maintained at the same time. However, when the entity delay duration is greater than 1 second, there is no time at which both machines are idle! The solution is to assign a separate DowntimeEntity to each machine so that they can be maintained separately.

Harry

[Cristiano Silva]

Expression Threshold ?

Atenciosamente,

Cristiano Luís Turbino de França e Silva

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[Harry King]

Jürgen,

On further reflection, this is actually a bug in ResourceUnit. It should not be possible for it to be assigned if it has a pending downtime event. This would allow both machines to start their maintenance at the same time. All other objects that implement maintenance and breakdowns, such as Server, work in this way.

Thank you for reporting this bug! I will include a fix for it in the next release.

Harry

[Jürgen Strohhecker]

Harry,

Thank you for your analysis and your help. In addition to this problem solved, I have learned more about DowntimeEntities. :-)

Best, Jürgen

[Harry King]

Jürgen,

The pending maintenance bug has been fixed in release 2021-06.

Harry