Dynamics Community Forum Thread Details

Dynamics 365 Business Central SaaS is proudly built-in on top of one of the highest Service Level Agreement (SLA) but it also requires its own service maintenance strategy. This is done in order to have the less downtime and its perception by the user and relative business processes.

This is generically described in the official documentation

FAQ About Using Business Central - Business Central | Microsoft Docs

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Both business functionality and service components are monitored continuously and updated as appropriate.

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And also referenced in

Service Overview for Business Central Online - Business Central | Microsoft Docs

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Business Central runs globally in many Microsoft Azure datacenters. All parts of the infrastructure and services are continually monitored and optimized to deliver the best possible experience. Most service operations and optimizations happen without users being aware of them. In some situations, user interaction is needed, like reconnecting to Business Central or refreshing the browser. Users will be notified directly in the browser if any action is required on their part. Users are asked to take action before the optimizations are applied on the service. This way, they can continue to work without further interruptions. Service operations happen all day, every day, to always provide best experience.

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These aforementioned service maintenances do have very low downtime and have its User Experience (UX) side expressed with the typical “sorry to bother you” message as shown below:

There is a second, probably a bit more hidden, service maintenance side effects that could impact integrations through REST and OData APIs, mainly.

When there is a whole cluster service maintenance that involves the whole infrastructure that wraps around the service tiers, these per definition cannot redirect traffic to another infrastructure to guarantee zero downtime nor emit signals around what is happening available to partner telemetries.

This is typically happening sporadically, during non-working business hours and for a very limited time - as much as possible -.

When this happens, if you have REST or OData API calls you might have them fail with an error message (HTTP 503) stating:

Tenant is under maintenance: Upgrade

Just as pure single example, performing a sampling of one AAD tenant operating in CET business hours (UTC+1) and per 30 days this happened.

Date	Time (UTC)	Duration (approx.)
17^th January	7 PM CET	4 min
28^th January	2 PM CET	6 min
29^th January	7 PM CET	12 min
31^st January	2 PM CET	10 min
1^st February	7 PM CET	2 min
3^rd February	7 PM CET	11 min

With a total of 116 requests reporting HTTP 503 in 30 days.

The solution to cope with service maintenance is to catch HTTP 503 error message and implement a retry logic, similar to what is described for HTTP 429 in the documentation

Working with API Limits in Dynamics 365 Business Central - Business Central | Microsoft Docs

If you would like this behavior to be changed and enhanced in future versions, you might think of vote for the following IDEAS

https://experience.dynamics.com/ideas/idea/?ideaid=b6444927-96c9-eb11-ba5e-0003ff45d51f

https://experience.dynamics.com/ideas/idea/?ideaid=d87720c9-6cfb-eb11-ba5e-0003ff45da2e