Replication
Overview
The Replication page contains a table that displays one WAL sender per row with configuration and current status information.
Data
- PID – The process ID of the WAL sender.
- App Name – Name of the application connected to the WAL sender process.
- User – Name of the user logged into the WAL sender process
- User ID – ID of the user logged into the WAL sender process
- Host – Host of the connected WAL receiver client.
- IP – IP address of the connected WAL receiver client.
- Port – Port of the connected WAL receiver client.
- State – Current WAL sender state.
- Backend Start – Time when the client first connected to the WAL sender.
- Synch State – Synchronous state of the standby server.
- Sync Priority – Priority of the current standby server client being chosen as the synchronous standby.
- Standby Lag – Number of WAL segments the standby server is behind as compared to the primary server. If this number increases, it means that the standby server is not able to keep up and replication may eventually be broken.
- Write Location - Last transaction log position written to disk by this standby server.
- Sent Location - Last transaction log position sent on this connection.
- Flush Location - Last transaction log position flushed to disk by this standby server.
- Replay Location - Last transaction log position replayed into the database on this standby server.
Actions
- Standby Lag (dwell) - Shows a time plot of the standby lag.
Admin Actions
Click the icon in the Delete table column to perform the following action:
- Delete – Delete the WAL Sender topology object if it becomes unnecessary. This will not affect the PostgreSQL server. Because the topology objects are persisted on the FMS, an object may become redundant or unnecessary if the WAL sender is no longer in use. You can manually delete it with this action. If it is still in use, the object will just be recreated.
Background Writer
Overview
The Background Writer page shows important configuration information as well as performance metrics related to the background writer.
Data
Top-left Table Section
- Health – Shows the overall health of the background writer.
- Alarms – Provides counts of the alarms for this agent, separated by severity.
- Last Stat Reset – Time when statistic counters for the background writer were last reset.
- Checkpoint Timeout – Maximum amount of time between automatic WAL checkpoint writes. If checkpoint segment limit is not reached before this time, a checkpoint will be triggered.
- BGWriter Delay – Delay between activity rounds for the background writer.
- BGWriter LRU Max Pages – Maximum number of pages written per activity round.
- BGWriter LRU Multiplier –Multiplier used to calculate the number of dirty buffers written for a given activity round
Graphs
- Total Buffers Allocated – Number of buffers allocated for use by the background writer.
- Buffer Write Comparison – Compares number of buffers written by a backend vs. being written by the background writer.
- Buffer Write Method Pct – Compares percent of buffers written by a backend vs. percent of buffers written during normal checkpoints.
- % of Checkpoints Required - Percent of checkpoints executed that were required. Low percent indicates system has not been active enough to reach WAL segment limit before reaching the checkpoint timeout limit.
- Checkpoint Interval – Average elapsed time between checkpoints. • Total Written Bytes Rate – Rate of total data written into Write Ahead Log.
- Avg Checkpoint Write Size – Average amount of data written into WAL during checkpoints.
- # of Time Reached Buffer Limit – Number of times the background writer stopped a cleaning scan because it had written too many buffers.
- Fsync Calls From Backends – Compares number of times a backend had to execute its own fsync call (normally handled by the background writer even when the backend does its own write).