Data Buffering

During normal operation, the Data Collector sends data and messages to the Historian Server using TCP/IP.The Server responds when it has successfully received the data.

Normal variations in response from the server can leave a small number of messages buffered in memory.When the collector loses its connection, or whenever the server cannot keep up with throughput, the data collector establishes a buffer. During such periods, the data collector continues to write data, caching it in the local file and memory buffer instead of writing it to the server. When the collector reestablishes the connection to the server, it forwards the stored data to the server, clearing the buffer as the server successfully receives the data.

If a collector writing to an archive loses its connection and the disk buffer becomes full, real-time collection does not begin immediately upon the re-established connection to the server. No data is collected from the time that the connection to the archive is re-established until approximately the time it takes for the buffer on the collector to clear.

Note: The Data Buffering feature does not apply to File collectors. The File collector does not process incoming files when the connection to the server is down. When the connection is re-established, processing of incoming files resumes.

If there is not enough free space for a collector to create its buffer files on initial startup, the collector shuts down immediately and sends the following message to the Event Viewer:

"[datetime] MessageAdd -MDW_iFIX collector Buffering could not create buffer files. Shutting down."

If there is not enough free space for the collector to create its buffer files on startup, the collector shuts down and sends a message to the Event Viewer. The simplest way to prevent this from happening is to free up disk space to allow the collector to start. If this is not possible, you can edit the Registry to change the buffer size.