Create a standby tenant|V4.1.0| docs|Distributed Database

Create a standby tenant

Last Updated：2023-08-01 06:02:28 Updated

You can create a standby tenant only by using the physical restore feature. To create a standby tenant, perform the following two steps: restore the standby tenant by using data backups and archive logs, and then change the recovery endpoint of the standby tenant.

Prerequisites

A standby tenant can be restored only by using the data backups and archive logs of the primary tenant and another standby tenant. Therefore, you must make sure that the following requirements are met before you create a standby tenant:

To restore a standby tenant by using the data backups and archive logs of the primary tenant, make sure that:
1. Archivelog is enabled for the primary tenant, and log archiving remains in the DOING state.
  
  For more information about how to enable archivelog, see Enable archivelog. For more information about how to view the log archiving status, see View the archiving progress.
  
  Notice
  
  To ensure that all logs during data backup are archived, you must enable archivelog for the primary tenant before you start data backup.
2. The data backup feature is enabled for the primary tenant and a full backup operation has been completed for the primary tenant.
  
  For more information about how to initiate full backup of a tenant, see Initiate a data backup job.
To restore a standby tenant by using the data backups and archive logs of another standby tenant, make sure that:
1. Archivelog is enabled for the source standby tenant, and log archiving remains in the DOING state.
  
  For more information about how to enable archivelog, see Enable archivelog. For more information about how to view the log archiving status, see View the archiving progress.
  
  Notice
  
  To ensure that all logs during data backup are archived, you must enable archivelog for the source standby tenant before you start data backup.
2. The data backup feature is enabled for the source standby tenant and a full backup operation has been completed for the source standby tenant.
  
  For more information about how to initiate full backup of a tenant, see Initiate a data backup job.

Restore a standby tenant

Log on to the sys tenant of the cluster where you want to create a standby tenant.
Execute the RESTORE statement to restore the standby tenant by using the data backups and archive logs of the sys tenant.

Syntax:
```
ALTER SYSTEM RESTORE standby_tenant_name FROM uri UNTIL TIME =timestamp WITH restore_option [DESCRIPTION description];
```
The parameters are as follows:
- standby_tenant_name: the name of the standby tenant to be restored.
- uri: the path of data backups and the path of archive logs of the primary tenant or an existing standby tenant.
- UNTIL TIME =timestamp: the recovery endpoint, which is the timestamp to which the standby tenant is restored. Join the parameter name and the value of timestamp with an equal sign ( =). The value of timestamp must be in the YYYY-MM-DD HH24:MI:SS.FF format, accurate to nanoseconds. For more information about to select timestamp, see Parameters related to physical restore.
- In restore_option, you can specify pool_list, locality, primary_zone, and kms_encrypt. pool_list is required and the others are optional.
Restore the restore_oracle_tenant tenant to the specified timestamp of 2022-11-11 15:04:23.825558 by using the logs archived in file:///data/1/nfs/backup//ob_backup_oracle_tenant/archive and the data backups stored in file:///data/1/nfs/backup//ob_backup_oracle_tenant/data. Set the resource pool to small_pool_2 and primary_zone to z1.

Sample statement:
```
ALTER SYSTEM RESTORE oracle_standby
  FROM 'file:///data/1/nfs/backup//ob_backup_oracle_tenant/archive,file:///data/1/nfs/backup//ob_backup_oracle_tenant/data' 
  UNTIL TIME='2022-11-11 15:04:23.825558' with 'pool_list=small_pool_2&primary_zone=z1';
```
For more information about the RESTORE statement, see Parameters related to physical restore.

You can query the oceanbase.CDB_OB_RESTORE_PROGRESS view for the restore progress. For more information, see Query the restore progress.

Change the recovery endpoint of the new standby tenant

The new standby tenant does not continuously synchronize the archive logs of the primary or source standby tenant. You must set the recovery endpoint of the new standby tenant by using the RECOVER statement.

Log on to the database as the administrator of the new standby tenant or the sys tenant of the cluster where the new standby tenant resides.
Execute the RECOVER statement to change the recovery endpoint of the standby tenant based on your actual business.
- Restore to a specified timestamp
```
ALTER SYSTEM RECOVER STANDBY [TENANT = tenant_name] UNTIL TIME='timestamp';
```
  You need to specify the name of the standby tenant by adding the TENANT = tenant_name parameter in the statement only if you execute the statement in the sys tenant. The timestamp parameter specifies the timestamp, in nanoseconds, to which the standby tenant is restored.
  
  After you execute this statement, the standby tenant is restored to the specified timestamp.
- Restore to a specified SCN
```
ALTER SYSTEM RECOVER STANDBY [TENANT = tenant_name] UNTIL SCN=scn;
```
  You need to specify the name of the standby tenant by adding the TENANT = tenant_name parameter in the statement only if you execute the statement in the sys tenant. The scn parameter specifies the system change number (SCN), which is a logical internal timestamp.
  
  After you execute this statement, the standby tenant is restored to the specified timestamp.
- Restore to an infinite endpoint
```
ALTER SYSTEM RECOVER STANDBY [TENANT = tenant_name] UNTIL UNLIMITED;
```
  You need to specify the name of the standby tenant by adding the TENANT = tenant_name parameter in the statement only if you execute the statement in the sys tenant. UNLIMITED indicates that the recovery endpoint is infinite.
  
  After you execute this statement, the standby tenant enters the continuous synchronization mode.

More information

Change the restore source of a standby tenant