The gp_master_mirroring table contains state information about the standby master host and its associated write-ahead log (WAL) replication process. If this synchronization process (gpsyncagent) fails on the standby master, it may not always be noticeable to users of the system. This catalog is a place where HAWQ administrators can check to see if the standby master is current and fully synchronized.

Table 1. pg_catalog.gp_master_mirroring

column type references description
summary_state text   The current state of the log replication process between the master and standby master - logs are either ‘Synchronized’ or ‘Not Synchronized’
detail_state text   If not synchronized, this column will have information about the cause of the error.
log_time timestamp with time zone   This contains the timestamp of the last time a master mirroring change occurred. For example, the timestamp when the value of summary_state changed from “Synchronized” to “Not Synchronized”. If no changes occur with regards to the standby master (it stays synchronized), the timestamp is not updated.
error_message text   If not synchronized, this column will have the error message from the failed synchronization attempt.