Question regarding steps from article on solving issue with MS-CDC table structure changes

[MoeE]

Hi,

I was reading through this article as our client is experiencing the same issue. The client has changed the base table structure and they are using MS-CDC so I was reading the relevant section that addresses this specific scenario from the article:

These steps are a little vague. Especially step 3.

I believe step 3 means to truncate the MS-CDC table on the source and not the actual source table.

Then in step 4, I believe the steps are to truncate the table on the target platform and then reload the data via QR. Is this correct?

Assistance with this is appreciated.

Thank you,

Mohammed

[john_wang]

Hello Mohammed, @MoeE 

The article appears to be accurate.

In Step 3, it refers to truncating the source table (EMPLOYEE2_table in the example), not the MS-CDC change table ([cdc].[dbo_EMPLOYEE2_table_CT]).

The CDC change table (__CT) will already have been dropped in Step 2.

Step 4 also appears to be correct.

Please feel free to let me know if I have overlooked anything.

thanks,
John.

[DesmondWOO]

Hi  @MoeE ,

You cannot truncate a source table while CDC is enabled. Therefore, you must first disable CDC for the table (Step 2) before performing the truncation (Step 3).

Regards,
Desmond

[MoeE]

Hi @DesmondWOO, @john_wang,

I see. My follow-up question is - What if the client cannot truncate the source database table as it contains important data?

I am admittedly confused about why the steps would recommend truncating the source tables.

Help understanding this is appreciated.

Thanks,

Mohammed

[john_wang]

Hello Mohammed, @MoeE 

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I see. My follow-up question is - What if the client cannot truncate the source database table as it contains important data?

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The article describes the procedure to be followed in the event that a customer decides to truncate the source table. It should not be interpreted as a request or recommendation from Qlik to truncate the table.

Hope this helps.

John.

[DesmondWOO]

Hi @MoeE ,

Regarding your case, I believe you should check 

the following two scenarios:

1. When the source table uses the DDL Change Handling feature.

2. When the source table uses the Alternate Source Table DDL Change Handling feature.

The main difference is that under the first scenario, the DDL change has already occurred. If you enable 'Capture DDL events' in the endpoint, the corresponding table will be suspended when a DDL change takes place.

Regards,
Desmond