> [!CAUTION]
> **Caution:** This documentation covers Edge for Private Cloud 4.51.00, which is no longer supported. Google does not provide security patches, bug fixes, or technical support for this version. The current supported version is 4.54.00. See the [Edge for Private Cloud documentation](https://docs.apigee.com/private-cloud/latest/overview) for the current version, or [All versions](https://docs.apigee.com/private-cloud/versions) to compare releases.

Perform the following during a PostgreSQL database failover:

1. Stop `apigee-postgresql` on the current master if it is still running:

   ```
   /opt/apigee/apigee-service/bin/apigee-service apigee-postgresql stop
   ```
2. Go to standby node and invoke the following command to make it the master:

   ```
   /opt/apigee/apigee-service/bin/apigee-service apigee-postgresql promote-standby-to-master IPorDNSofOldMaster
   ```

If old master is restored at some time in the future, make it a standby node:

1. On the current master, edit the config file to set:

   ```
   PG_MASTER=IPorDNSofNewMaster
   PG_STANDBY=IPorDNSofOldMaster
   ```

   > [!NOTE]
   > **Note:** Apigee strongly recommends that you use IP addresses rather than host names for the `PG_MASTER` and `PG_STANDBY` properties in your silent configuration file. In addition, you should be consistent on both nodes.
   >
   > If you use host names rather than IP addresses, you must be sure sure that the host names
   > properly resolve using DNS.

2. Enable replication on the new master:

   ```
   /opt/apigee/apigee-service/bin/apigee-service apigee-postgresql setup-replication-on-master -f configFIle
   ```
3. On the old master, edit the config file to set:

   ```
   PG_MASTER=IPorDNSofNewMaster
   PG_STANDBY=IPorDNSofOldMaster
   ```
4. Stop `apigee-postgresql` on the old master:

   ```
   /opt/apigee/apigee-service/bin/apigee-service apigee-postgresql stop
   ```
5. On the old master, clean out any old Postgres data:

   ```
   rm -rf /opt/apigee/data/apigee-postgresql/
   ```

   > [!NOTE]
   > **Note**: If necessary, you can backup this data before deleting it.

6. Configure the old master as a standby:

   ```
   /opt/apigee/apigee-service/bin/apigee-service apigee-postgresql setup-replication-on-standby -f configFile
   ```
7. On completion of replication, verify the replication status by issuing the following scripts on both servers. The system should display identical results on both servers to ensure a successful replication:
   1. On the master node, run:

      ```
      /opt/apigee/apigee-service/bin/apigee-service apigee-postgresql postgres-check-master
      ```

      Verify that it says it is the master.
   2. On the standby node:

      ```
      /opt/apigee/apigee-service/bin/apigee-service apigee-postgresql postgres-check-standby
      ```

      Verify that it says it is the standby.