Azure Monitor service limits

This article lists limits in different areas of Azure Monitor.

Alerts

Resource Default limit Maximum limit
Metric alerts (classic) 100 active alert rules per subscription. Call support
Metric alerts 5,000 active alert rules per subscription in Azure public, Azure China 21Vianet and Azure Government clouds. If you are hitting this limit, explore if you can use same type multi-resource alerts.
5,000 metric time-series per alert rule.
Call support.
Activity log alerts 100 active alert rules per subscription (cannot be increased). Same as default
Log alerts 512 active alert rules per subscription. 200 active alert rules per resource. Call support
Alert rules and Action rules description length Log search alerts 4096 characters
All other 2048 characters
Same as default

Alerts API

Azure Monitor Alerts have several throttling limits to protect against users making an excessive number of calls. Such behavior can potentially overload the system backend resources and jeopardize service responsiveness. The following limits are designed to protect customers from interruptions and ensure consistent service level. The user throttling and limits are designed to impact only extreme usage scenario and should not be relevant for typical usage.

Resource Default limit Maximum limit
GET alertsSummary 50 calls per minute per subscription Same as default
GET alerts (without specifying an alert ID) 100 calls per minute per subscription Same as default
All other calls 1000 calls per minute per subscription Same as default

Action groups

Resource Default limit Maximum limit
Azure app push 10 Azure app actions per action group. Same as Default
Email 1,000 email actions in an action group.
No more than 100 emails in an hour.
Also see the rate limiting information.
Same as Default
ITSM 10 ITSM actions in an action group. Same as Default
Logic app 10 logic app actions in an action group. Same as Default
Runbook 10 runbook actions in an action group. Same as Default
SMS 10 SMS actions in an action group.
No more than 1 SMS message every 5 minutes.
Also see the rate limiting information.
Same as Default
Voice 10 voice actions in an action group.
No more than 1 voice call every 5 minutes.
Also see the rate limiting information.
Same as Default
Webhook 10 webhook actions in an action group. Maximum number of webhook calls is 1500 per minute per subscription. Other limits are available at action-specific information. Same as Default

Autoscale

Resource Default limit Maximum limit
Autoscale settings 100 per region per subscription. Same as default
Autoscale profiles 20 profiles per autoscale setting. Same as default

Data collection rules

Limit Value
Maximum number of data sources 10
Maximum number of counter specifiers in performance counter 100
Maximum number of facility names in Syslog 20
Maximum number of XPath queries in Event Log 100
Maximum number of data flows 10
Maximum number of data streams 10
Maximum number of extensions 10
Maximum size of extension settings 32 Kb
Maximum number of Log Analytics workspaces 10

Log queries and language

General query limits

Limit Description
Query language Azure Monitor uses the same Kusto query language as Azure Data Explorer. See Azure Monitor log query language differences for KQL language elements not supported in Azure Monitor.
Azure regions Log queries can experience excessive overhead when data spans Log Analytics workspaces in multiple Azure regions. See Query limits for details.
Cross resource queries Maximum number of Application Insights resources and Log Analytics workspaces in a single query limited to 100.
Cross-resource query is not supported in View Designer.
Cross-resource query in log alerts is supported in the new scheduledQueryRules API.
See Cross-resource query limits for details.

User query throttling

Azure Monitor has several throttling limits to protect against users sending an excessive number of queries. Such behavior can potentially overload the system backend resources and jeopardize service responsiveness. The following limits are designed to protect customers from interruptions and ensure consistent service level. The user throttling and limits are designed to impact only extreme usage scenario and should not be relevant for typical usage.

Measure Limit per user Description
Concurrent queries 5 If there are already 5 queries running for the user, any new queries are placed in a per-user concurrency queue. When one of the running queries ends, the next query will be pulled from the queue and started. This does not include queries from alert rules.
Time in concurrency queue 3 minutes If a query sits in the queue for more than 3 minutes without being started, it will be terminated with an HTTP error response with code 429.
Total queries in concurrency queue 200 Once the number of queries in the queue reaches 200, any additional queries will by rejected with an HTTP error code 429. This number is in addition to the 5 queries that can be running simultaneously.
Query rate 200 queries per 30 seconds This is the overall rate that queries can be submitted by a single user to all workspaces. This limit applies to programmatic queries or queries initiated by visualization parts such as Azure dashboards and the Log Analytics workspace summary page.
  • Optimize your queries as described in Optimize log queries in Azure Monitor.
  • Dashboards and workbooks can contain multiple queries in a single view that generate a burst of queries every time they load or refresh. Consider breaking them up into multiple views that load on demand.
  • In Power BI, consider extracting only aggregated results rather than raw logs.

Log Analytics workspaces

Data collection volume and retention

Tier Limit per day Data retention Comment
Current Per GB pricing tier
(introduced April 2018)
No limit 30 - 730 days Data retention beyond 31 days is available for additional charges. Learn more about Azure Monitor pricing.
Legacy Free tiers
(introduced April 2016)
500 MB 7 days When your workspace reaches the 500 MB per day limit, data ingestion stops and resumes at the start of the next day. A day is based on UTC. Note that data collected by Azure Security Center is not included in this 500 MB per day limit and will continue to be collected above this limit.
Legacy Standalone Per GB tier
(introduced April 2016)
No limit 30 to 730 days Data retention beyond 31 days is available for additional charges. Learn more about Azure Monitor pricing.
Legacy Per Node (OMS)
(introduced April 2016)
No limit 30 to 730 days Data retention beyond 31 days is available for additional charges. Learn more about Azure Monitor pricing.
Legacy Standard tier No limit 30 days Retention can't be adjusted
Legacy Premium tier No limit 365 days Retention can't be adjusted

Number of workspaces per subscription.

Pricing tier Workspace limit Comments
Free tier 10 This limit can't be increased.
All other tiers No limit You're limited by the number of resources within a resource group and the number of resource groups per subscription.

Azure portal

Category Limit Comments
Maximum records returned by a log query 10,000 Reduce results using query scope, time range, and filters in the query.

Data Collector API

Category Limit Comments
Maximum size for a single post 30 MB Split larger volumes into multiple posts.
Maximum size for field values 32 KB Fields longer than 32 KB are truncated.

Search API

Category Limit Comments
Maximum records returned in a single query 500,000
Maximum size of data returned 64,000,000 bytes (~61 MiB)
Maximum query running time 10 minutes See Timeouts for details.
Maximum request rate 200 requests per 30 seconds per Azure AD user or client IP address See Rate limits for details.

Azure Monitor Logs connector

Category Limit Comments
Max number of records 500,000
Max query timeout 110 second
Charts Visualization in Logs page and the connector are using different charting libraries and some functionality isn't available in the connector currently.

General workspace limits

Category Limit Comments
Maximum columns in a table 500
Maximum characters for column name 500

Data ingestion volume rate

Azure Monitor is a high scale data service that serves thousands of customers sending terabytes of data each month at a growing pace. The volume rate limit intends to isolate Azure Monitor customers from sudden ingestion spikes in multitenancy environment. A default ingestion volume rate threshold of 500 MB (compressed) is defined in workspaces, this is translated to approximately 6 GB/min uncompressed -- the actual size can vary between data types depending on the log length and its compression ratio. The volume rate limit applies to data ingested from Azure resources via Diagnostic settings. When volume rate limit is reached, a retry mechanism attempts to ingest the data 4 times in a period of 30 minutes and drop it if operation fails. It doesn't apply to data ingested from agents or Data Collector API.

When data sent to your workspace is at a volume rate higher than 80% of the threshold configured in your workspace, an event is sent to the Operation table in your workspace every 6 hours while the threshold continues to be exceeded. When ingested volume rate is higher than threshold, some data is dropped and an event is sent to the Operation table in your workspace every 6 hours while the threshold continues to be exceeded. If your ingestion volume rate continues to exceed the threshold or you are expecting to reach it sometime soon, you can request to increase it in by opening a support request.

See Monitor health of Log Analytics workspace in Azure Monitor to create alert rules to be proactively notified when you reach any ingestion limits.

Note

Depending on how long you've been using Log Analytics, you might have access to legacy pricing tiers. Learn more about Log Analytics legacy pricing tiers.

Application Insights

There are some limits on the number of metrics and events per application, that is, per instrumentation key. Limits depend on the pricing plan that you choose.

Resource Limit Note
Total data per day 100 GB You can reduce data by setting a cap. If you need more data, you can increase the limit in the portal, up to 1,000 GB. For capacities greater than 1,000 GB, send email to AIDataCap@microsoft.com.
Throttling 32,000 events/second The limit is measured over a minute.
Data retention 30-730 days This resource is for Search, Analytics, and Metrics Explorer.
Availability multi-step test detailed results retention 90 days This resource provides detailed results of each step.
Maximum event size 64,000 bytes
Property and metric name length 150 See type schemas.
Property value string length 8,192 See type schemas.
Trace and exception message length 32,768 See type schemas.
Availability tests count per app 100
Profiler data retention 5 days
Profiler data sent per day 10 GB

For more information, see About pricing and quotas in Application Insights.

Next Steps