After you create a global database network (GDN), add secondary clusters to expand your database across regions. This page covers how to add a secondary cluster, remove one, and switch the primary cluster — including what happens to your data and connections during each operation.
Prerequisites
Before you begin, ensure that you have:
A GDN already created. For details, see Global Database Network (GDN).
Signed the Cross-border Data Transfer Compliance Agreement if the secondary cluster is in a region outside the Chinese mainland.
Limitations
Supported region pairs
GDN supports 10+ regions worldwide. The supported secondary cluster regions depend on where the primary cluster is located.
| Primary cluster region | Supported secondary cluster regions |
|---|---|
| Any region in the Chinese mainland | The same region as the primary cluster, or any other region in the Chinese mainland. For other region requirements, submit a ticket. |
| Any region outside the Chinese mainland | China (Hong Kong), Japan (Tokyo), South Korea (Seoul), Singapore, Malaysia (Kuala Lumpur), Indonesia (Jakarta), Philippines (Manila), Thailand (Bangkok), Germany (Frankfurt), US (Silicon Valley), US (Virginia), and UK (London). |
GDN constraints
A GDN supports one primary cluster and up to four secondary clusters.
All clusters in a GDN must use the same database engine version: Oracle syntax-compatible 2.0.
The node specifications of a secondary cluster must be greater than or equal to those of the primary cluster. For best performance, use matching specifications.
A cluster can belong to only one GDN at a time.
Unsupported features
Clusters in a GDN do not support:
Database and table restoration
Add a secondary cluster
Log on to the PolarDB console. In the left navigation pane, click Global Database Network (GDN).
On the Global Database Network (GDN) page, find the target GDN and click Add Secondary Cluster in the Actions column.
On the purchase page, configure the following parameters. For other parameters, see Custom purchase.
Parameter Description Region Select the region for the secondary cluster. For supported regions, see Supported region pairs. Creation Method Select Create Secondary Cluster. Global Database Network Select the target GDN. The GDN you selected in the previous step is pre-selected. Database Engine Must match the primary cluster: Oracle syntax-compatible 2.0. Compute Node Specifications Must match or exceed the primary cluster's specifications. To use higher specifications, upgrade on the cluster details page after creation. After the purchase completes, return to the Global Database Network (GDN) page. Click the Global Database Network ID of the target GDN to open its details page. The new secondary cluster appears in the Cluster List section.
Remove a secondary cluster
Removing a secondary cluster detaches it from the GDN and converts it into a standalone PolarDB cluster with full read/write capability. Use this operation when you no longer need cross-region replication for a particular cluster, or when you want to repurpose a secondary cluster independently.
After removal, the cluster cannot be re-added to any GDN as a secondary cluster. This action is irreversible.
Log on to the PolarDB console. In the left navigation pane, click Global Database Network (GDN).
On the Global Database Network (GDN) page, find the target GDN and click its Global Database Network ID to open the GDN details page.
In the Cluster List section, find the secondary cluster to remove and click Remove in the Actions column.
Read the notes in the dialog box and click OK.
The removal takes about 5 minutes. During this time:
Endpoints of all clusters in the GDN, including the cluster being removed, remain available.
Data synchronization between the removed cluster and the primary cluster continues until removal completes, then stops permanently.
After removal, the cluster switches to read/write mode as a standalone cluster.
Only secondary clusters can be removed from a GDN. The primary cluster cannot be removed.
Switch the primary cluster
Switching the primary cluster promotes a secondary cluster to primary. Use this operation for planned maintenance, such as migrating your primary workload to a different region. This is a controlled operation only — unplanned (forced) switchover is not supported.
Before you switch:
| Preparation item | Details |
|---|---|
| Timing | Perform the switch during off-peak hours. The operation causes a transient connection break of approximately 160 seconds. |
| Application reconnection | Make sure your application has an automatic reconnection mechanism. |
| Internet endpoint | If the original primary cluster has an Internet endpoint, verify that the new primary cluster also has one configured. Otherwise, your application may lose database access. For details, see View or apply for an endpoint. |
To switch the primary cluster:
Log on to the PolarDB console. In the left navigation pane, click Global Database Network (GDN).
On the Global Database Network (GDN) page, find the target GDN and click its Global Database Network ID to open the GDN details page.
In the Cluster List section, find the secondary cluster you want to promote and click Switch To Primary Cluster in the Actions column.
In the Primary/Secondary Switchover dialog box, select the secondary cluster to promote and click OK.
API reference
| API | Description |
|---|---|
| CreateDBCluster | Add a secondary cluster to a GDN. Set CreationOption to CreateGdnStandby and specify the GDNId. |
| RemoveDBClusterFromGDN | Remove a secondary cluster from a GDN. |
| SwitchOverGlobalDatabaseNetwork | Switch the primary cluster of a GDN. |
What's next
Global Database Network (GDN) — Learn about GDN architecture and common use cases.
Connect to a GDN — Learn how to connect to a global database network.