Task Failures

[Jolley]

Hi All!

Does anyone get these errors from time to time in QLIK Replicate? I've checked all servers invovlved in the QLIK processing and i don't see any trouble. No Network Packet loss, no SQL error messages, App server looks fine other than the .EXE for the task crashes so i see a temporary return of available RAM.

Any help\thoughts are greatly appreciated. Not urgent. The task restarts and processes all data successfully on its own.

00008876: 2022-08-04T12:11:15 [SOURCE_CAPTURE  ]E:  mssql_execute_log_lsn_peeper(...) failed upon SQLExecute with LSN parameters '0x00004938:0004f080:000f','0x00004938:0004f080:000f' [1020102]  (sqlserver_log_queries.c:816)

00008876: 2022-08-04T12:11:15 [SOURCE_CAPTURE  ]E:  Encountered an unexpeceted error. Aborting... [1020102]  (sqlserver_endpoint_capture.c:777)

[SwathiPulagam · Accepted solution]

Hi @Jolley ,

The error you encountered appears when Replicate doesn’t find the LSN on TLOG/backup log.

Thanks,

Swathi

[shashi_holla · Accepted solution]

Hi @Jolley 

The error is because the task was reading the data from the mentioned LSN and before it could complete, the LSN was moved. If we were reading from online logs and it got moved to Backup then in the next iteration it will read it from backup (if we have select Prefer Online Logs) as per the endpoint settings. Since we are not missing any data I think that's the setting and we should be good.

Thank you,

[Jolley · Accepted solution]

Hi Shashi!

Thank you very much! Just checked and T-LOG backups were running at this time. Thank you very much for your quick input and shedding light on this issue for us! Have a great day!

Bryan

[Jolley]

HI Swathi!

Thank you very much for the quick response! T-LOG backups were running at the same time! I'm assuming this was the cause and aver the task crashed it recovered and pulled the info from backup. Thanks again and have a great evening! Bryan

[lyka]

Hello,

To add on, this message means that it encountered a missing LSN - either it was purged or removed before Replicate was able to read it

We usually see this occur when the endpoint is using "Online logs only" 

If that is the case,  you need to use "Exclusively use sp_repldone within a single task" but that also means that you can only have 1 task running against that database and 1 running task.

Thanks

Lyka

[NakulanR]

Hi Support,

In the event that the error occurs during T-Log Backups, is there any endpoint/task configuration that can be put in place to prevent the task from throwing the recoverable error and instead log a warning? Or should tasks simply be stopped whilst the T-log backups are happening?

Regards,

Nak

[SushilKumar]

Hello @NakulanR 

team you need to understand Error are those which effect the change data capture and may leads to data mismatch. Would suggest to re visit the T log retention and backup policy for FIX.

You may make changes into Error settings under the Task setting as per your business requirement.

Regards,
Sushil Kumar 

[SachinB]

Hello @NakulanR ,

Handling errors during T-Log (Transaction Log) backups in SQL Server or other database systems is a critical task to ensure the integrity of your backups and avoid disruption in other processes.

Please follow the below community link 

holding-up-the-T-log

This method also requires the Log Reader Agent to be running to enable truncation of the Microsoft SQL Server active transaction log. Note that if the Log Reader Agent is not running, the active log may become full, causing the source database to be essentially "read-only" until the issue is resolved. 

Please refer the UG for more details.

Regards,

Sachin B

[NakulanR]

Hi @SachinB,

Apologies, I think my earlier explanation wasn't clear on the error.

The error is the "mssql_execute_log_lsn_peeper(...) failed upon SQLExecute with LSN parameters" error. This error appears in Replicate when the TLOG backups are happening on the source database, presumably because Replicate is searching through the online logs and they have been moved to the backup logs while Replicate is processing the log. Replicate is able to successfully recover by itself straight after the error, and we haven't seen any case of data loss.

We'd like to understand whether Replicate tasks need to be stopped while TLOG backups are happening to avoid the error appearing in Replicate for the scenario described above.

Thanks,

Nak