TN - HistCl26032302 - Troubleshooting Missing Historical Data

Description

Aveva Historian offers a variety of options to repair gaps or inaccuracies in Historical data. This article from InSource will review how to spot missing data and correct the gaps.

• Author: James Rochester
• Published: 9/23/2025
• Applies to: Aveva Historian 2023 +

 Details

Gaps in Historical data are generally observed as flat lines within a stream of data usually within Historian Trends.

First in order to verify whether the gap is legitimate or not there are a few things to consider. 

Method 1:

Were the Historian database and/or History blocks migrated to a new server?

If so verify whether the missing data exist on the actual date of migration. If this is the case this indicates that the current History block was moved while active which can lead to corruption. If you still have access to the pre migration system you can copy that History block and insert it in one of two ways:

Shutdown the Historian and Copy the Block into the Directory:

1. On the new or post-migration Historian Server In the Operations Control Management Console navigate to Historian>Management Console>Right click Status> Shutdown\disable Historian

2. On the old or pre-migration Historian server navigate to C:\Historian\Data\Circular and copy the affected History Block.

3. Copy the Block into the C:\Historian\Data\Circular on the new Historian server.

Migrate the block while the Historian is Active:

On the old or pre-migration Historian server navigate to C:\Historian\Data\Circular and copy the affected History Block.

On the new Historian Server copy the affected block into the C:\Historian\Data directory directly.

Then right click the block and drag it to the C:\Historian\Data\Circular directory and it will show a Move to Circular popup as below and you can move the affected block into the Circular Directory while the Historian is running. (You must move and not copy as the live system cannot handle copied files.)

Method 2:

If no migration occurred, we should first verify the data exist. We can do this by running the following query within Historian Query against the History Values View using the following query:

Getting all the values (historical data) stored to the specific tag 

SELECT Datetime, Tagname, Value FROM History WHERE Tagname = “Tagname”

(You can adjust the query to the specified time frame where the data is missing by adding the following to the end of the query or you can navigate to the time frame manually: WHERE DateTime BETWEEN '1996-07-01' AND '1996-07-31';)

If after running the Query you verify that data exist for the time frame correlating with the flat line exist please perform the following actions. 

1. Follow this article to backup your Windows Registry. Back up the registry manually 
2. In the Operations Control Management Console navigate to Historian>Management Console>Right click Status> Shutdown\disable Historian
    
3. Under [HKEY_LOCAL_MACHINE\SOFTWARE\ArchestrA\Historian\Programs\aahStorage] Create DWORD32 registry key named UseFileCacheForRetrieval and set it to zero.
4. Restart your PC.
    
5. In the Operations Control Management Console navigate to Historian>Management Console>Right click Status>Enable\Allow to run Historian

If this is successful in restoring the data this indicates that your Historian server does not have sufficient RAM and raising the amount of RAM the system has would help the retrieval, replication and storage to perform more robustly. Below is a chart showing the recommendations for Level 2 Plus Historian Servers.

Methods 3 & 4:
 These methods apply in either scenario and are covered in these InSource technical notes:

TN1286 - Rebuilding Historian Index

Resolving flat line in long duration Wonderware Historian Client Trends