# Perform scaling updates
<a name="scaling-updates"></a>

Scaling updates adjust the capacity of your compute environment by adding or removing instances. This is the fastest update strategy and doesn't require replacing existing instances. Scaling updates work with any service role type and allocation strategy, making them the most flexible update option.

## Changes that trigger a scaling update
<a name="scaling-updates-triggers"></a>

When you modify only the following settings, AWS Batch performs a scaling update. If you modify any of these settings along with other compute environment settings, AWS Batch performs an [infrastructure update](infrastructure-updates.md) instead.

The following settings trigger scaling updates when modified exclusively:
+ `desiredvCpus` – Sets the target number of vCPUs for the environment.
+ `maxvCpus` – Defines the maximum number of vCPUs that can be launched.
+ `minvCpus` – Specifies the minimum number of vCPUs to maintain.
+ `minScaleDownDelayMinutes` – Specifies minimum time (in minutes) that AWS Batch keeps instances running in the compute environment after their jobs complete.
**Note**  
`minScaleDownDelayMinutes` does not apply to instances being replaced during infrastructure updates.

For Fargate compute environments, you can also modify these settings for scaling updates:
+ `securityGroupIds` – Security group IDs for the compute environment.
+ `subnets` – Subnets for the compute environment.

**Note**  
We recommend not using `desiredvCpus` to initiate a scaling update as AWS Batch will dynamically adjust `desiredvCpus`. Instead you should update `minvCpus`.  
When updating `desiredvCpus`, the value must be between `minvCpus` and `maxvCpus`. The new value must be greater than or equal to the current `desiredvCpus`. For more information, see [Error message when you update the `desiredvCpus` setting](error-desired-vcpus-update.md).

**Important**  
If you modify any of these scaling settings together with other compute environment settings (such as instance types, AMI IDs, or launch templates), AWS Batch performs an infrastructure update instead of a scaling update. Infrastructure updates take longer and may replace existing instances.

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#### [ Performing scaling updates using the AWS Management Console ]

1. Open the AWS Batch console at [https://console.aws.amazon.com/batch/](https://console.aws.amazon.com/batch/).

1. In the navigation pane, choose **Environments** and then the **Compute environments** tab.

1. Select the compute environment to update.

1. Choose **Actions** and then **Edit**.

1. Modify one or more of the [settings that support scaling updates](#scaling-updates-triggers). For example:
   + For **Minimum vCPUs**, enter the minimum number of vCPUs.
   + For **Desired vCPUs**, enter the desired number of vCPUs.
   + For **Maximum vCPUs**, enter the maximum number of vCPUs.

1. Choose **Save changes**.

1. Monitor the compute environment status. The update should complete quickly since it only involves scaling operations.

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#### [ Performing scaling updates using the AWS CLI ]

Use the **update-compute-environment** command to perform scaling updates. The following two examples demonstrate common scaling operations. You can modify one or more of the following [settings that support scaling updates](#scaling-updates-triggers)
+ This example updates the desired, minimum, and maximum vCPUs:

  ```
  aws batch update-compute-environment \
      --compute-environment your-compute-environment-name \
      --compute-resources minvCpus=2,maxvCpus=8
  ```

------

## Monitoring scaling updates
<a name="scaling-updates-monitoring"></a>

Monitor your scaling updates using the AWS Batch console to view the compute environment status and check instance count and vCPU metrics. You can also use the AWS CLI with the **describe-compute-environments** command to check status and monitor instance counts and vCPU values.