# Ensure Multi-AZ Is Enabled for DMS Instances

- Source: https://support.icompaas.com/support/solutions/articles/62000233444-ensure-multi-az-is-enabled-for-dms-instances
- Section: [Solutions](https://support.icompaas.com/support/solutions) › [AWS Checks New Version](https://support.icompaas.com/support/solutions/62000112673) › [AWS New Checks](https://support.icompaas.com/support/solutions/folders/62000169206)
- Last updated: 2026-05-29
- Publisher: iCompaas, Inc. (https://www.icompaas.com)

**Profile Applicability** 

-   **Level 2**

#### **Description**

Enabling Multi-AZ for AWS Database Migration Service (DMS) instances ensures high availability and fault tolerance for your database migration tasks. With Multi-AZ enabled, a secondary replication instance is automatically created in a different Availability Zone to provide failover support in the event of a disruption to the primary instance.

#### **Rationale**

-   Improved Fault Tolerance: Provides a standby replication instance in a separate Availability Zone to maintain migration continuity.
    
-   Enhanced Availability: Reduces the risk of downtime by ensuring that DMS tasks can continue without manual intervention in the event of a failure.
    
-   Compliance: Aligns with best practices for high availability and disaster recovery.
    

#### **Impact**

**Pros:**

-   Ensures seamless failover during outages or disruptions.
    
-   Enhances system reliability and minimizes downtime.
    
-   Supports compliance with high availability requirements.
    

**Cons:**

-   May increase costs due to the creation and maintenance of a secondary instance.
    
-   Requires sufficient planning to configure and manage Multi-AZ instances.
    

#### **Default Value**

By default, Multi-AZ is disabled for DMS replication instances. It must be explicitly enabled during instance creation or modification.

#### **Pre-Requisite**

IAM Permissions Required:

-   dms:DescribeReplicationInstances
    
-   dms:ModifyReplicationInstance
    
-   AWS CLI installed and configured.
    

#### **Remediation**

**Test Plan:**

**Using AWS Console:**

1.  Sign in to the AWS Management Console.
    
2.  Navigate to Database Migration Service (DMS) > Replication Instances.
    
3.  For each replication instance, check the Multi-AZ field under the instance configuration. Ensure it is set to Yes.
    

**Using AWS CLI:**

1.  Describe the replication instance:  
    
    aws dms describe-replication-instances --filters Name=replication-instance-id,Values=<instance-id>
    
2.  Verify the MultiAZ field in the output. Ensure it is set to true.
    

**Implementation Steps:**

**Using AWS Console:**

1.  Navigate to Database Migration Service (DMS) > Replication Instances.![](https://support.icompaas.com/assets/kb/bdc9c36b39e0ac20.png)![](https://support.icompaas.com/assets/kb/cddcf3d5f2dc9383.png)
    
2.  Select the replication instance to update.![](https://support.icompaas.com/assets/kb/31ef99b81c07287d.png)
    
3.  Click Modify and enable Multi-AZ Deployment.![](https://support.icompaas.com/assets/kb/0bc1c43749c3081f.png)
    
4.  Save the changes.
    

**Using AWS CLI:**

1.  Enable Multi-AZ for the replication instance:  
    
    aws dms modify-replication-instance \\
    --replication-instance-arn <instance-arn> \\
    --multi-az
    

2.  Verify the updated configuration:  
    
    aws dms describe-replication-instances --filters Name=replication-instance-id,Values=<instance-id>
    

#### **Backout Plan**

#### **Using AWS Console:**

1.  #### If enabling Multi-AZ causes issues, sign in to the AWS Management Console.
    
2.  #### Navigate to AWS DMS, select the replication instance, and go to the Modify settings.  
    ![](https://support.icompaas.com/assets/kb/a94680642e98a618.png) ![](https://support.icompaas.com/assets/kb/26006f89449e0b70.png) ![](https://support.icompaas.com/assets/kb/016e7ed0c5974f7b.png)   
    
3.  #### Disable Multi-AZ by selecting No.![](https://support.icompaas.com/assets/kb/473a4d7087ee994f.png)
    
4.  #### Save the changes and confirm that the instance is now operating in a single Availability Zone.
    

#### **Using AWS CLI:**

1.  #### To disable Multi-AZ, run:  
    
    aws dms modify-replication-instance --replication-instance-arn <REPLICATION\_INSTANCE\_ARN> --multi-az false
    
2.  #### Verify that Multi-AZ has been disabled:  
    
    aws dms describe-replication-instances --replication-instance-arn <REPLICATION\_INSTANCE\_ARN>
    

#### **References**

-   [AWS DMS Replication Instance Documentation](https://docs.aws.amazon.com/dms/latest/userguide/CHAP_ReplicationInstance.html)
    
-   [Configuring Multi-AZ for DMS Instances](https://docs.aws.amazon.com/dms/latest/userguide/CHAP_BestPractices.html#CHAP_BestPractices.MA)
    
-   [AWS CLI Command Reference for DMS](https://docs.aws.amazon.com/cli/latest/reference/dms/index.html)

## Related compliance guidance

- [SOC 2 compliance: a practical implementation guide for cloud-native SaaS teams](https://support.icompaas.com/compliance/soc-2-trust-services-criteria): Configuration checks like this one are the technical half of a SOC 2 / ISO 27001 programme — the guide shows where they fit, what else an auditor expects, and how to evidence them.
- [ISO/IEC 27001:2022 compliance: a practical implementation guide](https://support.icompaas.com/compliance/iso-27001-2022): ISO 27001 Annex A.8 (technological controls) is where cloud hardening evidence lands; the guide shows how to run the ISMS around it.