Forum Discussion
Help me understand Fabric Capacity
Hi DamianMcc ,
nilendraFabric Thanks for your prompt response.Thanks for reaching out to the Microsoft Fabric Community forum.
Thank you for your detailed explanation of the situation. we understand that you're seeing a consumption of 193K CUs for a specific group of transactions and are expecting to have 345K CUs available for the next day.
However, your capacity might not reset all at once every 24 hours. Instead, it could be refilled gradually over time. For example, if your capacity is refilled gradually over time, you won't see an immediate full reset at the end of 24 hours.
Additionally, if there are other background processes or transactions that consume capacity, even if they are not visible to you, they could be affecting your available CUs.
To better estimate and manage CU usage, consider the following:
- Keep track of your CU usage every hour instead of just looking at the daily total.
- Watch out for sudden spikes—if any transaction uses more than 14,400 CUs in an hour, it might be using capacity from future hours.
- Adjust your CU usage by either increasing your capacity or spreading out transactions more evenly throughout the day.
Additonally you can refer the below Docs :
Understand the metrics app compute page - Microsoft Fabric | Microsoft Learn
Metrics app calculations - Microsoft Fabric | Microsoft LearnIf our response or a community member’s response addressed your query, please mark it as 'Accept Answer' and click 'Yes' if you found it helpful.
If you have any further questions, feel free to reach out.
Super Userhello DamianMcc
Let me clarify why it seems like you aren’t consuming your daily "limit" of 345,600 CUs (for an F4 SKU) but are still running out of capacity.
- consumption of 193K CUs reflects the total smoothed usage of your workloads over the day. This number doesn’t necessarily mean you’ve hit your theoretical daily maximum of 345,600 CUs.
- However, if your workloads frequently exceed the instantaneous limit of 4 CUs/second, Fabric starts borrowing from future capacity. This borrowing can lead to running out of capacity even before reaching the daily limit.
The theoretical daily limit assumes that usage is evenly distributed across all seconds in a day. In practice:- If your workloads create spikes (e.g., using more than 4 CUs/second during peak times), you’ll quickly deplete available capacity.
- Borrowing from future intervals leaves less capacity for subsequent operations, even if your total usage is below the daily allowance.
Thank you for responding.
I understand I am borrowing from future capacity. Beyond this single group of transactions consuming 193K of CU(s), there are no other transactions until they run again 24 hours later.
I'm still struggling to understand why, over those 24 hours between running these transactions, I am not 'gaining back' any capacity for the next day given this in theory I should have 345K of CU(s) to spend.
I'm obviously missing something, but how are we to estimate our usage this way?
v-aatheequeCommunity Support
Hi DamianMcc ,
nilendraFabric Thanks for your prompt response.Thanks for reaching out to the Microsoft Fabric Community forum.
Thank you for your detailed explanation of the situation. we understand that you're seeing a consumption of 193K CUs for a specific group of transactions and are expecting to have 345K CUs available for the next day.
However, your capacity might not reset all at once every 24 hours. Instead, it could be refilled gradually over time. For example, if your capacity is refilled gradually over time, you won't see an immediate full reset at the end of 24 hours.
Additionally, if there are other background processes or transactions that consume capacity, even if they are not visible to you, they could be affecting your available CUs.
To better estimate and manage CU usage, consider the following:
- Keep track of your CU usage every hour instead of just looking at the daily total.
- Watch out for sudden spikes—if any transaction uses more than 14,400 CUs in an hour, it might be using capacity from future hours.
- Adjust your CU usage by either increasing your capacity or spreading out transactions more evenly throughout the day.
Additonally you can refer the below Docs :
Understand the metrics app compute page - Microsoft Fabric | Microsoft Learn
Metrics app calculations - Microsoft Fabric | Microsoft LearnIf our response or a community member’s response addressed your query, please mark it as 'Accept Answer' and click 'Yes' if you found it helpful.
If you have any further questions, feel free to reach out.
- v-aatheeque
Hi DamianMcc ,
If our response addressed by the community member for your query, please mark it as Accept Answer and click Yes if you found it helpful.
Should you have any further questions, feel free to reach out.
Thank you for being a part of the Microsoft Fabric Community Forum!