Service Switchback in the DR Center After Fault Recovery

Services are migrated from the production center to the DR center due to a recoverable fault such as an unexpected power failure. After the production center recovers from the fault, you must synchronize data generated during the fault recovery period from the DR center to the production center and switch services back to the production center.

Prerequisites

Application-based protection policies and recovery plans have been configured for database applications or VMware vSphere and FusionCompute deployed on physical machines.
LUN-based protection policies and recovery plans have been configured for other applications.
For protected groups that use asynchronous remote replication, the DR center has at least one copy of intact service data.
The fault recovery of the recovery plan is successfully executed in the original DR center.
The datastore name cannot contain Chinese characters.

Procedure

Log in to the service system in the original production center and check the service startup status.
Ensure that the applications in the production center have been stopped before uninstalling disks.
- In scenarios where VMware VMs are deployed, you must connect vSphere Client to VMware vCenter in the production center to power off the protected VMs and remove them from the list.
- In scenarios where databases are deployed, you must manually close the applications in the production center.
Uninstall disks on application hosts.
In a VMware VM environment, you only need to uninstall datastores.

The purposes of uninstalling disks are to prevent application hosts from writing data into the disks in the service recovery process and to enable eReplication to report an error when disks are automatically mounted in the DR process.
Perform reprotection.
Data needs to be copied from the DR center to the production center to complete the initial data synchronization.
1. On the menu bar, select Utilization > Data Restore.
2. Select the recovery plan and click More > Reprotection on the Operation list.
3. Carefully read the content of the Confirm dialog box that is displayed and click OK to confirm the information.
If Save user configuration data is selected, self-defined protection policies and recovery settings, such as self-defined recovery steps, will be retained. Ensure that the configuration data has no adverse impact on service running after reprotection.
Test the recovery plan and clear the test data on eReplication. During the test, select a host or host group in the production center if necessary.
Before the services are switched back, you need to perform a DR test to verify the data availability to ensure that services can be successfully switched back. After the test, you must clear the test data to avoid switchback failure caused by test data. For details, see DR Testing in the DR Center.
On eReplication, perform a planned migration.
This step aims to switch services back to the production center from the DR center. After migration, data must be checked and test data must be cleared. For details, see 2 to 4 in Planned Migration of Services in the Production Center.
Before miagrating the protected groups in the SAP HANA cluster back, perform the following operations:
1. Use PuTTY to log in to the server at the DR end as user root.
2. Run the TMOUT=0 command to prevent PuTTY from exiting due to session timeout.
3. Run the su - sidadm command to switch to the user.
  sid indicates the SAP HANA System ID set when the user creates the database. The letter in the value is lowercase. In the following example, the value of sid is DB1.
  
  The following command output is displayed:
```
suse-hana:/ # su - db1adm
suse-hana:/usr/sap/DB1/HDB01>
```
4. Run the hdbsql -i xx -n localhost:3xx15 -u system -p PW -d sid command to log in to the database.
  xx is the value of Instance Number set when the database is created, and PW is set when the database is created.
  
  Password of the system user is based on the site requirements.
  
  The following command output is displayed:
```
suse-hana:/usr/sap/DB1/HDB01> hdbsql -i 01 -n localhost:30115 -u
system -p Password -d DB1
Welcome to the SAP HANA Database interactive terminal.
Type: \h for help with commands
\q to quit
hdbsql DB1=>
```
5. Run the alter system start database sid command to activate the database.
On eReplication, perform reprotection again.
Copy data from the production center to the DR center to recover the protected group status.