The license count in the Canary Historian is determined by the total number of tags in the most recent HDB file(s) of each DataSet, even if a tag is not receiving updates.

Each time a new HDB file is created, all tags that are part of the active logging sessions linked to that DataSet are recorded in the HDB file. Therefore, in order to remove a tag from using a Historian tag license, the logging session must be modified and the tag removed from it.  When this is complete, a new HDB file can be created without the tag in it.

When a tag has been released from the license count, all historical data records remain in the Canary Historian but are no longer accessible for client tools like Axiom, the Excel Add-in, and Web API.

Learn how to accomplish this for the OPC UA, OPC DA, and MQTT Data Collectors.

Releasing Tag Licenses from the OPC UA Collector

The UA logger can remove tags from the total tag license count by updating the last HDB file automatically.

Tag-Based Session

1. Open the Canary Admin. Select the OPC Collector tile.
2. Select the Configuration tab at the bottom.
3. Select a Session and navigate to the correct tag Group. Select a tag or tags (Shift and/or Control for multi select) by clicking on the tag row(s).  All selected tags should now be highlighted.
4. Select REMOVE in the top right corner. DO NOT SELECT REMOVE ABOVE THE SESSION LIST.
5. Click APPLY and then yes to make the change and restart the Logging Session.  All tags are now removed and the corresponding tag licenses are now free.

Selecting REMOVE under the Session Settings window will delete the entire session.

Path-Based Session

1. Open the Canary Admin. Select the OPC Collector tile.
2. Select the Configuration tab at the bottom.
3. Select the Session and ensure that the Sync Tags to Historian box is checked. Doing so will remove any tags from the Historian if they are no longer found in the OPC server or are disabled because of any filters being applied. This removal occurs whenever the collector performs its next browse, whether it be on session start or at a set time interval.

   

Releasing Tag Licenses from the OPC DA Collector

The OPC DA Collector must be configured to manually update the last HDB file.

1. Open the Logger Administrator application.
2. Select the Logging Session and then the Group tab associated with the tags you wish to delete.
3. Select one or more tags to delete (Shift key allows for mass selection). Press the Delete key on the keyboard. Select Apply.
4. You will be cautioned that for the change to take effect, you must ensure the Create new file when logging starts box must be checked and you must stop and then restart the Logging Session.
5. Now simply Stop and Start the Logging Session.

Releasing Tag Licenses from the MQTT Collector

1. Open the Canary Admin. Select the MQTT Collector tile.
2. Select the Configuration tab at the bottom.
3. Select the subscription branch and ensure that the Sync Tags to Historian box is checked. Doing so will automatically remove any tags from the Historian based upon the messages received from the broker.

   

Obsoleting Tags from the Historian

An additional method of releasing a tag license from the Historian is available in obsoleting the tag.  To obsolete tags from a Canary DataSet, follow these steps.

1. Remove the tag from the logging source, tags being actively logged cannot be obsoleted from the DataSet
2. Open the Canary Admin application, navigate to the Historian tile, select the appropriate DataSet, and navigate to the most recent HDB file
3. From within the HDB file, filter the tag list for the tags you wish to obsolete and download the list as a CSV file by selecting the downward arrow icon right of the filter box 
4. Uncheck the Include parent path feature 
5. Save the file locally
6. Within the Historian tile, navigate back to the view of all DataSets
7. Highlight the DataSet you wish to obsolete tags from and select the down arrow icon from the DATASET window, then choose OBSOLETE TAGS
8. Upload the CSV file with the list of tags you wish to obsolete and click ok

Remember, tags cannot be obsoleted if they are still being actively logged or accessed. You must stop logging on all tags you wish to obsolete prior to trying to remove them.

If the process is not successful, a .txt file will be generated with the reason the tags were not obsoleted.  That file will be created in the same folder as the CSV file you uploaded.  

The obsoleted tag(s) will still appear in the active HDB file, however they will be immediately removed from any client browsing.  Upon the start of a new HDB file, the tag(s) will no longer be listed.  You may manually force the rollover of the current HDB file if you wish to verify.