DOC-525 Migrate to Active-Active with Replica Of

content/rs/administering/creating-databases/create-active-passive.md

@@ -36,6 +36,8 @@ To configure a destination database as a Replica Of:
 1. Click ![icon_add](/images/rs/icon_add.png#no-click "Add") to show the box for the source database endpoint.
 1. Enter the URL of the source database endpoint:
 
+    <!-- Shared in migrate-to-active-active.md -->
+
     {{< note >}}
 The order of the Replica Of sources has no impact on replication.
     {{< /note >}}

content/rs/administering/database-operations/migrate-to-active-active.md

@@ -0,0 +1,96 @@
+---
+Title: Migrate a Database to Active-Active
+description:
+weight: $weight
+alwaysopen: false
+categories: ["RS"]
+---
+With [Active-Active databases]({{< relref "/rs/administering/designing-production/active-active.md" >}}), applications can read and write to the same data set from different geographical locations seamlessly and with latency less than 1 ms, without changing the way the application connects to the database.
+Active-Active databases also provide disaster recovery and accelerated data read-access for geographically distributed users.
+
+If you have data in a single-region Redis Enterprise Software database that you want to migrate to an Active-Active database,
+you'll need to create a new Active-Active database and migrate the data into the new database as a [Replica Of](https://docs.redislabs.com/latest/rs/administering/active-passive/) the existing database.
+This process will gradually populate the data in the Active-Active database.
+
+Before data migration starts, all data is flushed from the Active-Active database.
+The data is migrated to the Active-Active instance where you enabled Replica Of, and the data from that instance is copied to the other Active-Active instances.
+When data migration is finished, disable Replica Of and connect your applications to the Active-Active database.
+
+{{<image filename="images/rs/A-A_migration.png" width="75%" alt="Active-Active data migration process" >}}{{< /image >}}
+
+
+{{< note >}}
+During the migration, make sure that any applications that connect to the Active-Active database are **read-only**
+to make sure the dataset is identical to the source database during the migration process. You may continue to write to the source database during the migration process.
+{{< /note >}}
+
+To migrate an RS database to Active-Active:
+
+1. Create a new [Active-Active database]({{< relref "/rs/administering/creating-databases/create-active-active.md" >}}).
+
+    After the Active-Active database is activated, you see the database's configuration.
+
+1. Click **Edit** at the bottom of the database configuration.
+1. Enable **Migration using Replica Of**.
+1. Click **Continue** to confirm that you want to flush the data from the Active-Active database.
+1. Enter the URL of the source database endpoint (the order has no impact on replication).
+
+    <!-- Shared in create-active-passive.md -->
+
+    - For a source database in the same RS cluster - When you click on the box,
+    the available databases are shown in the correct format for the URL of the source endpoint:
+
+        ```sh
+        <database name>: redis://admin:<database_password>@<database_endpoint>:<database_port>
+        ```
+
+        You can select the database that you want to use as the source.
+
+    - For a source database in a different RS cluster:
+        1. Log in to the Web UI of the cluster that hosts the source database.
+        1. In **databases**, click on the database and go to **configuration**.
+        1. Under **Endpoint**, click on **Get Replica Of source URL**.
+
+            ![Replica Of source URL](/images/rs/replicaof-source-url.png)
+
+        1. Click **Copy to Clipboard** to copy the URL of the source endpoint.
+
+            If you want a different internal password, you can click **Regenerate Password**.
+
+            {{< warning >}}
+If you regenerate the password, replication to existing destinations fails until you update their configuration with the new password.
+            {{< /warning >}}
+
+        1. In the destination database, paste the URL of the source endpoint in the **Replica Of** box, and click ![Save](/images/rs/icon_save.png#no-click "Save").
+
+        {{< note >}}
+For a source database on a different Redis Enterprise Software cluster,
+you can [compress the replication data]({{< relref "/rs/administering/designing-production/active-passive#data-compression-for-replica-of">}}) to save bandwidth.
+        {{< /note >}}
+
+    - For a source database in an OSS Redis cluster - Enter the URL of the source endpoint in the format:
+
+        - If the database has a password -
+
+            ```sh
+            redis://:<redis_password>@<hostname>:<database_port>
+            ```
+
+            Where the password is the Redis password represented with URL encoding escape characters.
+
+        - If the database has no password -
+
+            ```sh
+            redis://<hostname>:<database_port>
+            ```
+
+    {{< note >}}
+If you used the mDNS protocol for the cluster name (FQDN),
+the [client mDNS prerequisites]({{< relref "/rs/installing-upgrading/configuring/mdns.md" >}}) must be met in order to communicate with other clusters.
+    {{< /note >}}
+
+1. Click **Update** at the bottom of the page.
+1. When the synchronization icon turns green ![Synchronization complete](/images/rs/icon_sync_green.png#no-click "Synchronization complete"), the migration is complete. Note that migration can take minutes to hours to complete depending on the dataset size and network quality.
+1. Edit the configuration of the Active-Active database and select the **Stop** button to disable **Migration using Replica Of**.
+{{<image filename="images/rs/Migration_using_Replica_Of_complete.png" alt="disable migration using replica of" >}} {{</image>}}
+1. Redirect your database connections to the Active-Active database.