Help Center/ Migration Center/ FAQs/ Storage Migration/ What Can I Do If Flow Control Is Triggered During Migration?
Updated on 2026-05-22 GMT+08:00
What Can I Do If Flow Control Is Triggered During Migration?
If a large number of migration tasks fail and error 503 is recorded in the failure object list, the flow control may be triggered. You can handle the issue as follows:
- Check whether flow control is triggered at the source.
- If it is, contact technical support of the source platform or submit a service ticket to increase the flow control limit.
- If it is not, contact technical support of the target platform or submit a service ticket to increase the flow control limit.
- (Optional) Adjust the maximum number of concurrent subtasks in the migration workflow. Reducing the maximum number of concurrent subtasks may decrease the migration speed.
- Click the workflow name to view its details.
- Click the corresponding resource name. View the Migration Progress area.
- Click Modify above Expected Concurrent Subtasks and configure an appropriate value. There cannot be more than 10 concurrent subtasks for each online migration node. For example, if there are 2 online migration nodes, there can be up to 20 subtasks.

- Click Confirm.
- Retry the migration workflow.
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