Note: XCONLY: The following description applies only to Postgres-XC.
CREATE BARRIER is new SQL query specific to Postgres-XC since 0.9.5 that creates a new XLOG record on each node of the cluster consistently. Barrier is created via a 2PC like mechanism from a remote Coordinator in 3 phases with a prepare, execute and ending phases. A new recovery parameter called recovery_target_barrier has been added in recovery.conf. In order to perform a complete PITR recovery, it is necessary to set recovery_target_barrier to the value of a barrier already created. Then distribute recovery.conf to each data folder of each node, and then to restart the nodes one by one.
Default barrier name is dummy_barrier_id. It is used when no barrier name is specified when using CREATE BARRIER.
GTM restart port for this barrier can be backed up at GTM and GTM standby. To activate this, set the variable gtm_backup_barrier to on.