How to synchronize column lengths on source to CDC Task?

[AgusBudianto]

Hello

Let me ask you a question. I'm planning to increase the column length of the source varchar (10) to varchar 100. What should I do in the Qlik Replicate task? We used a Log Stream Task before the Target Table Task.

Thanks, You

[SachinB]

Hello @AgusBudianto 

If you change the datatype or column length of a table that is already part of an active CDC replication, no changes are required at the Qlik Replicate task level. Once the alteration is made on the source system, Replicate automatically captures and applies the change (provided DDL replication is supported and enabled).

Qlik Replicate automatically changes the metadata of the target table to reflect DDL statements performed on the source endpoint.

Supported DDL statements include:

• Create table
• Drop table
• Rename table
• Add column
• Drop column
• Rename column
• Change column data type

For more information, Please follow the below link

DDLStatements 

Regards,
Sachin B

[AgusBudianto]

Hi @SachinB 

Thanks, you for your reply

Previously I had Task is:

1. Source to Target Logs Stream Change Processing Mode: Transactional apply -> (no changes are required?)
2. Logs Stream to Target Store Changes Processing Task DDL options: Ignore -> (no changes are required or need stop and resume task ?)
3. Logs Stream to Target Apply Changes Settings Task When source table is altered: ALTER target table -> (no changes are required?)

How for DDL target? Need to change length also? because poin 2 for Target Store Changes Processing Task DDL options: Ignore

Regards,
Anto

[SachinB]

Hello @AgusBudianto ,

When the DDL handling option is set to Ignore, Qlik Replicate ignores all DDL operations and does not apply any metadata changes to the target.

To ensure that source DDL changes are reflected on the target, you must configure When source table is altered to ALTER TARGET TABLE, which allows Replicate to apply the corresponding schema changes on the target.

When the DDL option is set to Ignore:

• Qlik Replicate will NOT apply DDL changes to the target.

• Any increase in the source column length will not be automatically reflected on the target.

• CDC will continue only if the new data fits into the existing target column length.

• If the source data exceeds the target length, the task will fail or the data will be truncated, depending on the target behaviour.

Regards,
Sachin B

[AgusBudianto]

Hi @SachinB 

So, if the DDL handling option is set to Ignore, do I have to stop and resume the CDC task and manually set the target column length?

So, what are the best practices?

Regards,

Anto

[SachinB · Accepted solution]

Hello @AgusBudianto ,

Yes. If you choose the DDL handling option as Ignore, any metadata changes made at the source must be manually applied to the target tables.

In such cases, you should stop the task, alter the target table metadata accordingly, and then resume the task. This process must be followed every time there is a metadata change in the source system to avoid data mismatches or CDC failures.

Let me know in case if you have additional queries for the same.

Regards,
Sachin B

[AgusBudianto]

Ok @SachinB, so no need to make any changes to Log stream task or CDC task, just stop both tasks, then change the length target table and resume both tasks again.

[SachinB]

Hello @AgusBudianto ,

Yes, you are right.

Regards,
Sachin B

[AgusBudianto]

Thanks you @SachinB