Enabling Master Mirroring

You can configure a new Greenplum Database system with a standby master using gpinitsystem or enable it later using gpinitstandby. This topic assumes you are adding a standby master to an existing system that was initialized without one.

For information about the utilities gpinitsystem and gpinitstandby, see the Greenplum Database Utility Guide.

To add a standby master to an existing system

Ensure the standby master host is installed and configured: gpadmin system user created, Greenplum Database binaries installed, environment variables set, SSH keys exchanged, and that the data directories and tablespace directories, if needed, are created.
Run the gpinitstandby utility on the currently active primary master host to add a standby master host to your Greenplum Database system. For example:
```
$ gpinitstandby -s smdw
```
Where -s specifies the standby master host name.

To switch operations to a standby master, see Recovering a Failed Master.

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

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

$ gpstate -f

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

For information about the gpstate utility, see the Greenplum Database Utility Guide.