Changed a Gateway name—and yesterday’s trend vanished?
Imagine opening a factory temperature trend and finding that it displays only today's readings. Yesterday's history appears to have vanished. If someone recently changed the Ignition Gateway System Name, however, the problem might be in how records are linked and queried—not in the underlying stored values.
This is a document-based educational explanation, not a reproduced production incident.
Missing from a chart does not necessarily mean deleted
Think of a library whose books have been re-catalogued. Searching only the old catalogue can make a book look missing even though it is still on the shelf.
Ignition's SQL Tag Historian associates recorded values with a driver entry that identifies the originating Gateway and Tag Provider. The manufacturer's documentation describes those associations in the sqlth_drv table.
After a Gateway System Name change, new recordings can be associated with a different driver entry. Earlier entries are not automatically linked to the new ones. As a result, a historian query or chart may display only data collected after the change. That visible gap alone does not prove the earlier rows were erased.
A hypothetical example
| Concept | Before rename | After rename |
|---|---|---|
| Gateway name | LINE_A | LINE_MAIN |
| Historian driver link | Previous driver entry | Different driver entry |
| Trend output | Earlier readings appear | Only new readings may appear |
| Was original history deleted? | Not determined | Not determined |
The names and behavior in this table are illustrative. They do not represent real observed driver IDs, industrial measurements or a laboratory test.
A read-only first checklist
- Check approved change records. Did the Gateway System Name change, and when?
- Identify the historian type. The documented
sqlth_drvbehavior is specifically relevant to SQL Tag Historian. Do not generalize it to all history backends. - Compare history references. Use an authorized read-only process to identify whether historical queries point to different driver identities.
- Escalate before SQL changes. The vendor recommends contacting support before changing
sqlth_drvtable entries; do not edit database mappings as a casual troubleshooting step.
A Gateway rename can also affect remote historian providers, alarm journal integrations, security zones and other name-based references. Restoring a chart view alone is not evidence that every dependency has been checked.
Takeaway
A missing-looking trend and deleted historical records are different findings. Verify the source and the query link before making an operational change.
Primary sources
- Ignition 8.3 System Name Usage Reference
- Ignition Database Table Reference: sqlth_drv
- Ignition Gateway Settings
Evidence limits: This educational article interprets manufacturer documentation. Examples are hypothetical, not measured tests on production equipment, databases or customer workspaces. It reports no measured detection, recovery or processing outcome. Operational changes require authorization and the documentation for the actual product and version.