small updates

Author: EdB-MSFT

articles/azure-monitor/essentials/prometheus-api-promql.md

@@ -38,7 +38,7 @@ To set up Azure Active Directory authentication, follow the steps below:
 1. To register an app, follow the steps in [Register an App to request authorization tokens and work with APIs](../logs/api/register-app-for-token.md?tabs=portal)
 
 ### Allow your app access to your workspace
-Allow your app to query data from your Azure Monitor workspace.
+Assign the *Monitoring Data Reader* role your app so it can query data from your Azure Monitor workspace.
 
 1. Open your Azure Monitor workspace in the Azure portal.
 
@@ -78,7 +78,7 @@ curl -X POST 'https://login.microsoftonline.com/<tennant ID>/oauth2/token' \
 --data-urlencode 'grant_type=client_credentials' \
 --data-urlencode 'client_id=<your apps client ID>' \
 --data-urlencode 'client_secret=<your apps client secret' \
---data-urlencode 'resource= https://prometheus.monitor.azure.com'
+--data-urlencode 'resource=https://prometheus.monitor.azure.com'
 ```
 
 Sample response body:
@@ -204,6 +204,13 @@ The following limitations are in addition to those detailed in the Prometheus sp
 
 For more information on Prometheus metrics limits, see [Prometheus metrics](../../azure-monitor/service-limits.md#prometheus-metrics)
 
+> [!NOTE]
+> Azure managed Prometheus is  **case insensitive**. If one time series differs from another only by the casing of a string - metric name, label name, label value etc, it is treated the same time series. This behavior differs from native open source Prometheus which is a case sensitive system. For example, the following two time series are threated as the same time series in Azure managed Prometheus:  
+> `diskSize(cluster=”eastus”, node=”node1”, filesystem=”usr_mnt”)`   
+> `diskSize(cluster=”eastus”, node=”node1”, filesystem=”usr_MNT”)`  
+> For more information on scraping and case sensitivity, see [Customize scraping of Prometheus metrics in Azure Monitor](./prometheus-metrics-scrape-configuration.md#case-sensitivity)
+
+
 ## Next steps
 
 [Azure Monitor workspace overview (preview)](./azure-monitor-workspace-overview.md)  

articles/azure-monitor/essentials/prometheus-metrics-scrape-configuration.md

@@ -11,6 +11,24 @@ ms.reviewer: aul
 
 This article provides instructions on customizing metrics scraping for a Kubernetes cluster with the [metrics addon](prometheus-metrics-enable.md) in Azure Monitor.
 
+## Case sensitivity
+Azure managed Prometheus is a case insensitive system. If one time series differs from another only by a difference in the case of a string - metric name, label name, label value etc, it is treated as the same time series. This behavior is different from native open source Prometheus which is a case sensitive system.   
+
+In Azure managed Prometheus the follow time series are considered the same: 
+
+  `diskSize(cluster=”eastus”, node=”node1”, filesystem=”usr_mnt”)`  
+  `diskSize(cluster=”eastus”, node=”node1”, filesystem=”usr_MNT”)` 
+
+The above examples are a single  time series in time series database.
+-	Any samples ingested against them will be stored as if they are scraped/ingested against a single time series.
+-	If the examples above are ingested with the same timestamp, one of them will be dropped randomly.
+-	The casing that will be stored in the time series database and returned in query, is unpredictable. Different casing at different times for the same time series may be returned.
+-	Any metric name or label name/value matcher present in the query, will be retrieved from time series database by making a case-insensitive comparison. If there is a case sensitive matcher in a query, it is automatically treated as a case-insensitive matcher when making string comparisons.
+
+It is best practice to insure that a time series is produced/scraped only in 1 unique casing.
+
+In OSS Prometheus the above time series are treated as two different time series. Any samples scraped/ingested against them will be stored separately.
+
 ## Configmaps
 
 Three different configmaps can be configured to change the default settings of the metrics addon: