You can calculate the replication lag by comparing the current WAL write location on the primary with the last WAL location received/replayed by the standby. They can be retrieved using pg_current_xlog_location on the primary and the pg_last_xlog_receive_location/pg_last_xlog_replay_location on the standby, respectively.
I am a newbee to Postgresql and I want to build replication between master and slave servers(8.4). I was able to set it up but I cannot check archive# at master and slave servers as what was the last archive# generated at master and what is current archive# at Slave server that is being replayed.
Is there any view in PostgreSQL with which I can find the details of Archive# generation at Master and archive# that is replaying currently or last/recent archive# that has replayed at slave server.
So can you please provide me the commands as how to check the last archive# is generated at master and slave(being replayed), lag between master and slave servers.