Extended Trend logs stop updating on the Enterprise Server

[Product_Support]

Issue

Extended Logs have stopped updating on the Enterprise Server.

Product Line

EcoStruxure Building Operation

Environment

• EcoStruxure Building Operation
• Enterprise Server
• Automation Server
• Trend Logs (TL)
• Extended Trend Logs (ETL)

Architecture Note

In typical deployments, Trend Logs reside on Automation Servers, while Extended Trend Logs are hosted on the Enterprise Server. Data is transferred from TL to ETL using a subscription-based mechanism driven by sequence numbers. Any inconsistency in this synchronization can result in ETL not updating even when TL continues logging.

Cause

• Extended Trend logs have been configured on-site and have been operating reliably over an extended period. A subset or all of the Extended Trend Logs has stopped updating.
• The issue can occur after a Server backup is restored. 
• Trend logs and Extended Trend logs are allocated sequence numbers, and if the sequence numbers do not follow the correct sequence, the Extended Trend log may not update.

How to verify the issue:

Trend Log:

1. Navigate to the corresponding Trend log and open it in a "Trend Log List" view.
2. Add an additional column to show the Sequence number.
3. Note the highest sequence number used.

Extended Trend Log:

1. Navigate to the Extended Trend log that is referencing the above Trend Log.
2. Open the Extended Trend Log properties.
3. Press and hold down the "ALT" key and click where the dot is indicated on the screen shot below, (just below the Basic tab). 
4. This will show some more properties for the Extended Trend Log, the one you are interested in is “Last transferred sequence number”.
    

If the last transferred sequence number on the Extended Trend Log is higher than the Trend log’s highest sequence number, then that is why the Extended Trend Log has stopped.

Resolution

Option 1 - When Historical Data is Required

• Increase the sample interval by reducing the interval time of the Trend log until it has caught up with Extended Trend Log's Sequence Number.
• The Extended Trend Log will only fetch new records that has a sequence number higher than the last transferred sequence number.
• Until the sequence of Trend Log has caught up with the sequence of Extended Trend Log, you will not see any new records in the Extended Trend Log.
• The Log records that are created after you have caught up in sequence numbers will only be fetched to Extended Trend Log.

Option 2 - When Historical Trend and Extended Trend Data Are Not Required

Create a new Extended Trend Log and associate the corresponding Trend Log. The new Extended Trend Log will fetch every record that the Trend log has and continue from there, but you will lose the records of the old Extended Trend Log had that the Trend log does not have anymore.

Option 3 - When Historical Trend Data Is Not Required but Extended Trend Data Must Be Retained

Backup & restore the AS on the same AS. The Trend log will be cleared but the Extended Trend Log will start fetching new records.

Important Note - Extended Trend Log: 

• The extended trend log cannot log a variable.
• The extended trend log gets the initial value of the connected trend log.
• Do not connect more than one extended trend log to a trend log or another extended trend log. If a trend log is connected to two or more extended trend logs, critical conflicts can occur.
• The extended trend log must have the same unit as the monitored trend log to correctly display values.