# Limit

+ `tidb_store_limit` : Control the number of request sent to one TiKV node at the same time to prevent a single TiKV node from timing out or return errors due to the large number of request exceeding its processing capacity.


![left](./student-guide/diagram/06-limit-01-01.png)

+ `tidb_retry_limit` : Controls the number of retries for optimistic transactions. Optimistic transactions will be retried when they encounter transaction conflicts, but too many retries will exacerbate conflicts, resulting in performance degradation. Too few retries will reduce the success rate of transaction execution.

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Limit
- tidb_store_limit
  - Control the number of request sent to one TiKV node at the same time to prevent a single TiKV node from timing out or return errors due to the large number of request exceeding its processing capacity
- tidb_retry_limit
  - Control the number of retries of optimistic transactions. Optimistic transactions will be retried when they encounter transaction conflicts, but too many retries will exacerbate conflicts, resulting in performance degradation. Too few retries will reduce the success rate of transaction execution