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Setting a global system variable runtime value normally requires the SYSTEM_VARIABLES_ADMIN privilege (or the deprecated SUPER  privilege). For more information, see Section 5.1.9.1, “System Variable Privileges” . 

Clone variables are configured on the recipient MySQL server instance where the cloning operation is executed. 

## • clone_autotune_concurrency 

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When clone_autotune_concurrency  is enabled (the default), additional threads for remote cloning operations are spawned dynamically to optimize data transfer speed. The setting is applicable to recipient MySQL server instance only. 

During a cloning operation, the number of threads increases incrementally toward a target of double the current thread count. The effect on the data transfer speed is evaluated at each increment. The process either continues or stops according to the following rules: 

•If the data transfer speed degrades more than 5% with an incremental increase, the process stops. 

•If there is at least a 5% improvement after reaching 25% of the target, the process continues. Otherwise, the process stops. 

•If there is at least a 10% improvement after reaching 50% of the target, the process continues. Otherwise, the process stops. 

•If there is at least a 25% improvement after reaching the target, the process continues toward a new target of double the current thread count. Otherwise, the process stops. 

The autotuning process does not support decreasing the number of threads. 

The clone_max_concurrency  variable defines the maximum number of threads that can be spawned. 

If clone_autotune_concurrency  is disabled, clone_max_concurrency  defines the number of threads spawned for a remote cloning operation. 

## • clone_buffer_size 

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