What is the impact on qlik replication (extract) if there are insert made in the source database, inserts that are made in 'nologging' ?

[lmarville]

Hello,

What is the influence on the replication task when the nologging mode is used for inserts ?

Thanks,

Louis

[john_wang]

Hello Louis, @lmarville ,

I'm assuming you are talking about Oracle source database.

Qlik Replicate is log-based CDC replication solution, it reads/parses Oracle archived and online redo log files to capture interesting changes and applies them to target endpoints. 

Well, it looks the 'NOLOGGING' parameter is a little confusing and depends on the type of DML being done (and other settings eg Oracle database archive log mode etc).  'NOLOGGING' does not mean there is, eh, nothing logged but only a small set of information is written to the redo log. Only when doing 'append' type of operations logging can be disabled. If NOLOGGING is set on a table and you do 'direct load' inserts or inserts with an append hint, it might not be logged , because no such information were recorded into redo log files,  and Replicate will not see the changes. anyway , regular DML *is* always logged and will always be noticed and replicated by Replicate.

Please be careful do not leave 'NOLOGGING' option on in a production database or tables because the conventional recovery strategy is no longer applicable. 

The best practice to work with Oracle source database please see Ensure that ARCHIVELOG mode is on and supplemental logging . 

Hope this helps.

Regards,

John.

[lmarville]

Thank you John for your informative reply. We should make our query more precise :

"is the force logging mandatory on the Oracle source for QLIK Replicate? Can QLIK replicate changes made in direct  (append) load ?".

Oracle Reference : 

https://www.orafaq.com/wiki/Nologging_and_force_logging

Thank you for your time.

[john_wang · Accepted solution]

Hello Louis,

No, the force logging is unnecessary at all for Qlik Replicate.

Regards,

John.