Qlik Replicate Task Fails to Resume Post-Upgrade – LSN Not Found Error

[ANANDKUMAR]

We are encountering an issue with Qlik Replicate after performing an upgrade. Below are the details:

• Source Endpoint: SQL Managed Instance (SQL MI)
• Target Endpoint: SQL Managed Instance (SQL MI) 
• Task Type: Microsoft SQL Server
• Upgrade Activity: Qlik Replicate upgrade was performed. As part of the process, all tasks were stopped.
• Downtime Duration: Approximately 15–30 minutes
• Issue Observed: After the upgrade, when attempting to resume the task, it fails with the following error:

Error Message:
LSN '000005C4:000004A0:000A' could not be found, neither in the transaction log nor in the backup log.
Timestamp: 2025-09-23 04:40:42

Temporary Workaround:

Reloading the target resolves the issue, but this is not ideal for large datasets or production environments.

Request:

• Is there any alternative to reloading the target to recover from this LSN error?
• Can Qlik Replicate be configured to handle such scenarios more gracefully post-upgrade?
• Are there best practices to avoid LSN loss during upgrade windows?

[narendersarva]

Hi @ANANDKUMAR 

After the upgrade please try to start the task with simple resume instead of running from timestamp. This tells Replicate to resume from the point the log is currently at. Also, please ensure enough log backup history is retained to cover your planned maintenance window and try to configure backup log reading.

Hope this helps.

Thanks
Naren

[ANANDKUMAR]

Hi @narendersarva 

Thanks for your response. Just to clarify, I did resume the task after the upgrade, but it failed with the LSN not found error. So I’m not resuming from timestamp; I’m using the default resume option.

Could you please confirm if by “simple resume” you mean the default resume behavior in the UI? If so, that’s already what I’m doing.

Also, could you guide me on how to verify or configure “backup log reading” for SQL MI endpoints in Qlik Replicate? I’d like to ensure that’s enabled to avoid similar issues in future upgrades.

Appreciate your help!

[john_wang]

Hello @ANANDKUMAR ,

I’m not sure which endpoint you’re using, but please note that in SQL Managed Instance (SQL MI) the transaction log (TLOG) is truncated every 5–10 minutes. Qlik Replicate can read from the online TLOG, but it cannot access the backup TLOG. If interruptions last longer than this grace period, Replicate will be unable to resume from the previous stream position.

Possible solutions:

1. As you mentioned, reload the task.

2. Alternatively, use the MS-CDC endpoint, which does not require access to the TLOG. MS-CDC endpoint may introduce more limitations, for more detailed information please check User Guide MS-CDC Limitations and considerations.

Hope this help.

John.