# Enabling MSDTC
Use the following process to enable MSDTC for your DB instance:
1. Create a new option group, or choose an existing option group.
1. Add the `MSDTC` option to the option group.
1. Create a new parameter group, or choose an existing parameter group.
1. Modify the parameter group to set the `in-doubt xact resolution` parameter to 1 or 2.
1. Associate the option group and parameter group with the DB instance.
## Creating the option group for MSDTC
Use the AWS Management Console or the AWS CLI to create an option group that corresponds to the SQL Server engine and version of your DB instance.
**Note**
You can also use an existing option group if it's for the correct SQL Server engine and version.
### Console
The following procedure creates an option group for SQL Server Standard Edition 2016.
**To create the option group**
1. Sign in to the AWS Management Console and open the Amazon RDS console at [https://console.aws.amazon.com/rds/](https://console.aws.amazon.com/rds/).
1. In the navigation pane, choose **Option groups**.
1. Choose **Create group**.
1. In the **Create option group** pane, do the following:
1. For **Name**, enter a name for the option group that is unique within your AWS account, such as **msdtc-se-2016**. The name can contain only letters, digits, and hyphens.
1. For **Description**, enter a brief description of the option group, such as **MSDTC option group for SQL Server SE 2016**. The description is used for display purposes.
1. For **Engine**, choose **sqlserver-se**.
1. For **Major engine version**, choose **13.00**.
1. Choose **Create**.
### CLI
The following example creates an option group for SQL Server Standard Edition 2016.
**To create the option group**
+ Use one of the following commands.
**Example**
For Linux, macOS, or Unix:
```
aws rds create-option-group \
--option-group-name msdtc-se-2016 \
--engine-name sqlserver-se \
--major-engine-version 13.00 \
--option-group-description "MSDTC option group for SQL Server SE 2016"
```
For Windows:
```
aws rds create-option-group ^
--option-group-name msdtc-se-2016 ^
--engine-name sqlserver-se ^
--major-engine-version 13.00 ^
--option-group-description "MSDTC option group for SQL Server SE 2016"
```
## Adding the MSDTC option to the option group
Next, use the AWS Management Console or the AWS CLI to add the `MSDTC` option to the option group.
The following option settings are required:
+ **Port** – The port that you use to access MSDTC. Allowed values are 1150–49151 except for 1234, 1434, 3260, 3343, 3389, and 47001. The default value is 5000.
Make sure that the port you want to use is enabled in your firewall rules. Also, make sure as needed that this port is enabled in the inbound and outbound rules for the security group associated with your DB instance. For more information, see [Can't connect to Amazon RDS DB instance](CHAP_Troubleshooting.md#CHAP_Troubleshooting.Connecting).
+ **Security groups** – The VPC security group memberships for your RDS DB instance.
+ **Authentication type** – The authentication mode between hosts. The following authentication types are supported:
+ Mutual – The RDS instances are mutually authenticated to each other using integrated authentication. If this option is selected, all instances associated with this option group must be domain-joined.
+ None – No authentication is performed between hosts. We don't recommend using this mode in production environments.
+ **Transaction log size** – The size of the MSDTC transaction log. Allowed values are 4–1024 MB. The default size is 4 MB.
The following option settings are optional:
+ **Enable inbound connections** – Whether to allow inbound MSDTC connections to instances associated with this option group.
+ **Enable outbound connections** – Whether to allow outbound MSDTC connections from instances associated with this option group.
+ **Enable XA** – Whether to allow XA transactions. For more information on the XA protocol, see [XA specification](https://publications.opengroup.org/c193).
+ **Enable SNA LU** – Whether to allow the SNA LU protocol to be used for distributed transactions. For more information on SNA LU protocol support, see [Managing IBM CICS LU 6.2 transactions](https://docs.microsoft.com/en-us/previous-versions/windows/desktop/ms685136(v=vs.85)) in the Microsoft documentation.
### Console
**To add the MSDTC option**
1. Sign in to the AWS Management Console and open the Amazon RDS console at [https://console.aws.amazon.com/rds/](https://console.aws.amazon.com/rds/).
1. In the navigation pane, choose **Option groups**.
1. Choose the option group that you just created.
1. Choose **Add option**.
1. Under **Option details**, choose **MSDTC** for **Option name**.
1. Under **Option settings**:
1. For **Port**, enter the port number for accessing MSDTC. The default is **5000**.
1. For **Security groups**, choose the VPC security group to associate with the option.
1. For **Authentication type**, choose **Mutual** or **None**.
1. For **Transaction log size**, enter a value from 4–1024. The default is **4**.
1. Under **Additional configuration**, do the following:
1. For **Connections**, as needed choose **Enable inbound connections** and **Enable outbound connections**.
1. For **Allowed protocols**, as needed choose **Enable XA** and **Enable SNA LU**.
1. Under **Scheduling**, choose whether to add the option immediately or at the next maintenance window.
1. Choose **Add option**.
To add this option, no reboot is required.
### CLI
**To add the MSDTC option**
1. Create a JSON file, for example `msdtc-option.json`, with the following required parameters.
```
{
"OptionGroupName":"msdtc-se-2016",
"OptionsToInclude": [
{
"OptionName":"MSDTC",
"Port":5000,
"VpcSecurityGroupMemberships":["sg-0abcdef123"],
"OptionSettings":[{"Name":"AUTHENTICATION","Value":"MUTUAL"},{"Name":"TRANSACTION_LOG_SIZE","Value":"4"}]
}],
"ApplyImmediately": true
}
```
1. Add the `MSDTC` option to the option group.
**Example**
For Linux, macOS, or Unix:
```
aws rds add-option-to-option-group \
--cli-input-json file://msdtc-option.json \
--apply-immediately
```
For Windows:
```
aws rds add-option-to-option-group ^
--cli-input-json file://msdtc-option.json ^
--apply-immediately
```
No reboot is required.
## Creating the parameter group for MSDTC
Create or modify a parameter group for the `in-doubt xact resolution` parameter that corresponds to the SQL Server edition and version of your DB instance.
### Console
The following example creates a parameter group for SQL Server Standard Edition 2016.
**To create the parameter group**
1. Sign in to the AWS Management Console and open the Amazon RDS console at [https://console.aws.amazon.com/rds/](https://console.aws.amazon.com/rds/).
1. In the navigation pane, choose **Parameter groups**.
1. Choose **Create parameter group**.
1. In the **Create parameter group** pane, do the following:
1. For **Parameter group family**, choose **sqlserver-se-13.0**.
1. For **Group name**, enter an identifier for the parameter group, such as **msdtc-sqlserver-se-13**.
1. For **Description**, enter **in-doubt xact resolution**.
1. Choose **Create**.
### CLI
The following example creates a parameter group for SQL Server Standard Edition 2016.
**To create the parameter group**
+ Use one of the following commands.
**Example**
For Linux, macOS, or Unix:
```
aws rds create-db-parameter-group \
--db-parameter-group-name msdtc-sqlserver-se-13 \
--db-parameter-group-family "sqlserver-se-13.0" \
--description "in-doubt xact resolution"
```
For Windows:
```
aws rds create-db-parameter-group ^
--db-parameter-group-name msdtc-sqlserver-se-13 ^
--db-parameter-group-family "sqlserver-se-13.0" ^
--description "in-doubt xact resolution"
```
## Modifying the parameter for MSDTC
Modify the `in-doubt xact resolution` parameter in the parameter group that corresponds to the SQL Server edition and version of your DB instance.
For MSDTC, set the `in-doubt xact resolution` parameter to one of the following:
+ `1` – `Presume commit`. Any MSDTC in-doubt transactions are presumed to have committed.
+ `2` – `Presume abort`. Any MSDTC in-doubt transactions are presumed to have stopped.
For more information, see [in-doubt xact resolution server configuration option](https://docs.microsoft.com/en-us/sql/database-engine/configure-windows/in-doubt-xact-resolution-server-configuration-option) in the Microsoft documentation.
### Console
The following example modifies the parameter group that you created for SQL Server Standard Edition 2016.
**To modify the parameter group**
1. Sign in to the AWS Management Console and open the Amazon RDS console at [https://console.aws.amazon.com/rds/](https://console.aws.amazon.com/rds/).
1. In the navigation pane, choose **Parameter groups**.
1. Choose the parameter group, such as **msdtc-sqlserver-se-13**.
1. Under **Parameters**, filter the parameter list for **xact**.
1. Choose **in-doubt xact resolution**.
1. Choose **Edit parameters**.
1. Enter **1** or **2**.
1. Choose **Save changes**.
### CLI
The following example modifies the parameter group that you created for SQL Server Standard Edition 2016.
**To modify the parameter group**
+ Use one of the following commands.
**Example**
For Linux, macOS, or Unix:
```
aws rds modify-db-parameter-group \
--db-parameter-group-name msdtc-sqlserver-se-13 \
--parameters "ParameterName='in-doubt xact resolution',ParameterValue=1,ApplyMethod=immediate"
```
For Windows:
```
aws rds modify-db-parameter-group ^
--db-parameter-group-name msdtc-sqlserver-se-13 ^
--parameters "ParameterName='in-doubt xact resolution',ParameterValue=1,ApplyMethod=immediate"
```
## Associating the option group and parameter group with the DB instance
You can use the AWS Management Console or the AWS CLI to associate the MSDTC option group and parameter group with the DB instance.
### Console
You can associate the MSDTC option group and parameter group with a new or existing DB instance.
+ For a new DB instance, associate them when you launch the instance. For more information, see [Creating an Amazon RDS DB instance](USER_CreateDBInstance.md).
+ For an existing DB instance, associate them by modifying the instance. For more information, see [Modifying an Amazon RDS DB instance](Overview.DBInstance.Modifying.md).
**Note**
If you use an domain-joined existing DB instance, it must already have an Active Directory domain and AWS Identity and Access Management (IAM) role associated with it. If you create a new domain-joined instance, specify an existing Active Directory domain and IAM role. For more information, see [Working with AWS Managed Active Directory with RDS for SQL Server](USER_SQLServerWinAuth.md).
### CLI
You can associate the MSDTC option group and parameter group with a new or existing DB instance.
**Note**
If you use an existing domain-joined DB instance, it must already have an Active Directory domain and IAM role associated with it. If you create a new domain-joined instance, specify an existing Active Directory domain and IAM role. For more information, see [Working with AWS Managed Active Directory with RDS for SQL Server](USER_SQLServerWinAuth.md).
**To create a DB instance with the MSDTC option group and parameter group**
+ Specify the same DB engine type and major version as you used when creating the option group.
**Example**
For Linux, macOS, or Unix:
```
aws rds create-db-instance \
--db-instance-identifier mydbinstance \
--db-instance-class db.m5.2xlarge \
--engine sqlserver-se \
--engine-version 13.00.5426.0.v1 \
--allocated-storage 100 \
--manage-master-user-password \
--master-username admin \
--storage-type gp2 \
--license-model li \
--domain-iam-role-name my-directory-iam-role \
--domain my-domain-id \
--option-group-name msdtc-se-2016 \
--db-parameter-group-name msdtc-sqlserver-se-13
```
For Windows:
```
aws rds create-db-instance ^
--db-instance-identifier mydbinstance ^
--db-instance-class db.m5.2xlarge ^
--engine sqlserver-se ^
--engine-version 13.00.5426.0.v1 ^
--allocated-storage 100 ^
--manage-master-user-password ^
--master-username admin ^
--storage-type gp2 ^
--license-model li ^
--domain-iam-role-name my-directory-iam-role ^
--domain my-domain-id ^
--option-group-name msdtc-se-2016 ^
--db-parameter-group-name msdtc-sqlserver-se-13
```
**To modify a DB instance and associate the MSDTC option group and parameter group**
+ Use one of the following commands.
**Example**
For Linux, macOS, or Unix:
```
aws rds modify-db-instance \
--db-instance-identifier mydbinstance \
--option-group-name msdtc-se-2016 \
--db-parameter-group-name msdtc-sqlserver-se-13 \
--apply-immediately
```
For Windows:
```
aws rds modify-db-instance ^
--db-instance-identifier mydbinstance ^
--option-group-name msdtc-se-2016 ^
--db-parameter-group-name msdtc-sqlserver-se-13 ^
--apply-immediately
```
## Modifying the MSDTC option
After you enable the `MSDTC` option, you can modify its settings. For information about how to modify option settings, see [Modifying an option setting](USER_WorkingWithOptionGroups.md#USER_WorkingWithOptionGroups.ModifyOption).
**Note**
Some changes to MSDTC option settings require the MSDTC service to be restarted. This requirement can affect running distributed transactions.