Merge pull request #309556 from yutanglin16/patch-25

Clarify assigned instances and always ready settings

Author: prmerger-automator[bot]

articles/app-service/manage-automatic-scaling.md

@@ -185,6 +185,17 @@ Azure App Service uses Application Request Routing cookies known as an ARR Affin
 
 To disable ARR Affinity cookies: select your App Service app, and under **Settings**, select **Configuration**. Next select the **General settings** tab. Under **Session affinity**, select **Off** and then select the **Save** button.
 
+### Why does my App Service plan show more assigned instances than the always ready settings in my apps?
+
+This can happen when the plan’s assigned instances are higher than the highest always ready instance count used by any app in the plan. The assigned instances represent the minimum number of instances the plan must run. If this value is higher than the always ready values, the plan continues to use that minimum.
+
+To correct this configuration, update the always ready instance count for any app in the plan. You must change the value. Saving the same value does not trigger recalculation. After the update, the plan sets its assigned instance count to the highest always ready value across all apps in the plan.
+
+You must complete this update by using [CLI](#set-the-minimum-number-of-web-app-instances) or Azure Resource Manager API. The Azure portal does not apply the recalculation correctly at this time.
+
+**Example:** A plan may have 7 assigned instances. The apps in the plan may have always ready values of 2, 3, and 5. Billing is based on 7 because that is the minimum number of instances. If you change any app’s always ready value, for example from 3 to 4, the plan recalculates. It then sets its assigned instance count to 5, which is the highest always ready value.
+
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