# Enable a CDC stream for an existing table in Amazon Keyspaces
<a name="keyspaces-enable-cdc-alter-table"></a>

To enable a CDC stream for an existing table, you can use the `ALTER TABLE` statement in CQL, the `update-table` command with the AWS CLI, or you can use the console.

For each changed row in the table, Amazon Keyspaces can capture the following changes based on the `view_type` of the `cdc_specification` you select:
+ `NEW_AND_OLD_IMAGES` – both versions of the row, before and after the change. This is the default.
+ `NEW_IMAGE` – the version of the row after the change.
+ `OLD_IMAGE` – the version of the row before the change.
+ `KEYS_ONLY` – the partition and clustering keys of the row that was changed.

For information about how to tag a stream, see [Add new tags to a stream](Tagging.Operations.existing.stream.md).

**Note**  
Amazon Keyspaces CDC requires the presence of a service-linked role (`AWSServiceRoleForAmazonKeyspacesCDC`) that publishes metric data from Amazon Keyspaces CDC streams into the `"cloudwatch:namespace": "AWS/Cassandra"` in your CloudWatch account on your behalf. This role is created automatically for you. For more information, see [Using roles for Amazon Keyspaces CDC streams](using-service-linked-roles-CDC-streams.md).

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#### [ Cassandra Query Language (CQL) ]

**Enable a stream (CDC stream) with CQL**

You can use `ALTER TABLE` to enable a stream for an existing table.

1. The following example creates a stream that only captures changes to partition and clustering keys of a changed row.

   ```
   ALTER TABLE mykeyspace.mytable
   WITH cdc = TRUE
   AND CUSTOM_PROPERTIES={'cdc_specification': {'view_type': 'KEYS_ONLY'}};
   ```

1. To verify the stream settings, you can use the following statement.

   ```
   SELECT keyspace_name, table_name, cdc, custom_properties FROM system_schema_mcs.tables WHERE keyspace_name = 'mykeyspace' AND table_name = 'mytable';
   ```

   The output of the statement looks similar to this.

   ```
    keyspace_name | table_name | cdc  | custom_properties
   ---------------+------------+------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
       mykeyspace |    mytable | True | {'capacity_mode': {'last_update_to_pay_per_request_timestamp': '1741385897045', 'throughput_mode': 'PAY_PER_REQUEST'}, 'cdc_specification': {'latest_stream_arn': 'arn:aws:cassandra:us-east-1:111122223333:/keyspace/mykeyspace/table/mytable/stream/2025-03-07T22:20:10.454', 'status': 'ENABLED', 'view_type': 'KEYS_ONLY'}, 'encryption_specification': {'encryption_type': 'AWS_OWNED_KMS_KEY'}, 'point_in_time_recovery': {'status': 'disabled'}}
   ```

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#### [ CLI ]

**Create a CDC stream with the AWS CLI**

1. To create a stream for an existing table you can use the following syntax.

   ```
   aws keyspaces update-table \
   --keyspace-name 'mykeyspace' \
   --table-name 'mytable' \
   --cdc-specification status=ENABLED,viewType=NEW_AND_OLD_IMAGES
   ```

1. The output of that command shows the standard `create-table` response and looks similar to this example.

   ```
   { "resourceArn": "arn:aws:cassandra:us-east-1:111122223333:/keyspace/mykeyspace/table/mytable" }
   ```

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#### [ Console ]

**Enable a CDC stream with the Amazon Keyspaces console**

1. Sign in to the AWS Management Console, and open the Amazon Keyspaces console at [https://console.aws.amazon.com/keyspaces/home](https://console.aws.amazon.com/keyspaces/home).

1. In the navigation pane, choose **Tables**, and then choose a table from the list.

1. Choose the **Streams** tab.

1. Choose **Edit** to enable a stream.

1. Select **Turn on streams**.

1. Choose **View type** of the stream. The following options are available. Note that you can't change the view type of a stream after it's been created.
   + **New and old images** – Amazon Keyspaces captures both versions of the row, before and after the change. This is the default.
   + **New image** – Amazon Keyspaces captures only the version of the row after the change.
   + **Old image** – Amazon Keyspaces captures only the version of the row before the change.
   + **Primary key only** – Amazon Keyspaces captures only the partition and clustering key columns of the row that was changed.

1. To finish, choose **Save changes**.

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