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Buffering and High Availability

PI Buffer Subsystem statistics

  • Last UpdatedJul 15, 2025
  • 2 minute read

These global counters record PI Buffer Subsystem's overall status, which includes all buffering from a given client or interface computer. They include counters that are not specific to any one server, and counters that represent aggregated values of all servers receiving buffered data.

Attribute

Description

Buffer Sessions Active

Number of active buffer sessions1 for physical servers to which PI Buffer Subsystem is connected and sending data.

Buffer Sessions Offline

Number of inactive buffer sessions1 for physical servers for which PI Buffer Subsystem is unable queue and/or send data.

Buffer Sessions Total

Total number of active and offline buffer sessions1.

Compressed Events/sec

Rate of events marked for archiving (does not include Out-Of-Order events).

Events In Error

Number of events not processed locally by the Buffer Subsystem, including:

  • events with invalid mode, data type, or value

  • events that can't be coerced to the point's data type

  • events with a digital set that does not match the point's configuration

    These events are still sent to the Data Archive servers.

Events Received/sec

Rate of events received.

Events Rejected

Number of events rejected by the Buffer Subsystem, including:

  • events with unsupported API source type (uncommon)

  • the target server is version 3.4.375 and PI Buffer Subsystem does not have write access to the point

    These events are not sent to the Data Archive servers.

Health

Overall health (0 = OK, 1 = Warning, 2 = Error, 3=Critical)

Out-Of-Order Events/sec

Rate of out-of-order events received.

Point Count

Numbers of local points with cached configuration (on disk).

Point Edits/sec

Rate of new points and point edits received from all servers.

Points With Post Error

Total number of points that received errors when posting, for all servers.

Queue> Capacity

The estimated time (in seconds) that PI Buffer Subsystem can buffer data for this logical server if the connection to all servers is lost.

Queue> File Count

Total number of queue files for all servers.

Queue> Reset Folder Count

Number of buffer queue reset folders currently in storage. If PI Buffer Subsystem detects the queue is corrupted and is not able to recover it, a new queue is created so that data can flow. Each time that happens, the old corrupted queue files are saved in a separate folder under the configured queue path.

Queue> Write Errors

Number of events that failed to be written to the buffer queue for all servers.

Total API Buffered Events

Number of events in all API buffers (including APIBUF*.DAT files).

Total Events Sent/sec

Rate of events sent to all servers.

Total Queue Writes Exclusive/sec

Rate of events written to a buffer queue but not other queues in the same collective (no fanning mode).

Total Queue Writes/sec

Rate of events written to all buffer queues.

Total Queued Events

Total buffered events.

Total Snapshot Posts/sec

Rate of data posts to all PI sessions.

Unresolved Cache Points

Numbers of local points with unknown configuration.

1 When PI Buffer Subsystem establishes buffering to a physical server, it creates a buffer session. The session persists as long as PI Buffer Subsystem is buffering to this server.

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