Restoring Coordinator Mirroring After a Recovery

To restore the coordinator mirroring after a recovery
To restore the coordinator and standby instances on original hosts (optional)
To check the status of the coordinator mirroring process (optional)

After you activate a standby coordinator for recovery, the standby coordinator becomes the primary coordinator. You can continue running that instance as the primary coordinator if it has the same capabilities and dependability as the original coordinator host.

You must initialize a new standby coordinator to continue providing coordinator mirroring unless you have already done so while activating the prior standby coordinator. Run gpinitstandby on the active coordinator host to configure a new standby coordinator. See Enabling Coordinator Mirroring.

You can restore the primary and standby coordinator instances on the original hosts. This process swaps the roles of the primary and standby coordinator hosts, and it should be performed only if you strongly prefer to run the coordinator instances on the same hosts they occupied prior to the recovery scenario.

Important Restoring the primary and standby coordinator instances to their original hosts is not an online operation. The coordinator host must be stopped to perform the operation.

For information about the LightDB-A Database utilities, see the LightDB-A Database Utility Guide.

Parent topic: Recovering a Failed Coordinator

To restore the coordinator mirroring after a recovery

Ensure the original coordinator host is in dependable running condition; ensure the cause of the original failure is fixed.
On the original coordinator host, move or remove the data directory, gpseg-1. This example moves the directory to backup_gpseg-1:
```
$ mv /data/coordinator/gpseg-1 /data/coordinator/backup_gpseg-1
```
You can remove the backup directory once the standby is successfully configured.
Initialize a standby coordinator on the original coordinator host. For example, run this command from the current coordinator host, scdw:
```
$ gpinitstandby -s cdw
```
After the initialization completes, check the status of standby coordinator, cdw. Run gpstate with the -f option to check the standby coordinator status:
```
$ gpstate -f
```
The standby coordinator status should be passive, and the WAL sender state should be streaming.

To restore the coordinator and standby instances on original hosts (optional)

Note Before performing the steps in this section, be sure you have followed the steps to restore coordinator mirroring after a recovery, as described in the To restore the coordinator mirroring after a recoveryprevious section.

Stop the LightDB-A Database coordinator instance on the standby coordinator. For example:
```
$ gpstop -m
```
Run the gpactivatestandby utility from the original coordinator host, cdw, that is currently a standby coordinator. For example:
```
$ gpactivatestandby -d $COORDINATOR_DATA_DIRECTORY
```
Where the -d option specifies the data directory of the host you are activating.
After the utility completes, run gpstate with the -b option to display a summary of the system status:
```
$ gpstate -b
```
The coordinator instance status should be Active. When a standby coordinator is not configured, the command displays No coordinator standby configured for the standby coordinator state.
On the standby coordinator host, move or remove the data directory, gpseg-1. This example moves the directory:
```
$ mv /data/coordinator/gpseg-1 /data//backup_gpseg-1
```
You can remove the backup directory once the standby is successfully configured.
After the original coordinator host runs the primary LightDB-A Database coordinator, you can initialize a standby coordinator on the original standby coordinator host. For example:
```
$ gpinitstandby -s scdw
```
After the command completes, you can run the gpstate -f command on the primary coordinator host, to check the standby coordinator status.

To check the status of the coordinator mirroring process (optional)

You can run the gpstate utility with the -f option to display details of the standby coordinator host.

$ gpstate -f

The standby coordinator status should be passive, and the WAL sender state should be streaming.

For information about the gpstate utility, see the LightDB-A Database Utility Guide.