Does Qlik Replicate read the transaction log when SQL Server MS-CDC is the source?

[MoeE]

Hi,

When a Qlik Replicate task has SQL Server as the source with MS-CDC, is Qlik reading the transaction log or is it reading the change tables created by MS-CDC?

I know when MS-Replication is enabled, QR will read the transaction log. Is it different with MS-CDC.

Regards,

Mohammed

[MoeE · Accepted solution]

Hi,

It looks like I've found the answer. According to the SQL Server (MS-CDC) source endpoint documentation

"When replicating data from Microsoft SQL Server using MS-CDC, changes are captured from Microsoft Change Tables as opposed to the SQL Server transaction log"

Thanks,

Mohammed

[john_wang]

Hello Mohammed, @MoeE 

This is correct. Thanks for the update.

Best Regards,

John.

[MoeE]

Hi John,

Can you please confirm something for me? If SQL Server using MS-CDC is the source, can QR capture and apply updates to tables without any primary keys or indexes on the source table?

The documentation seems to suggest this in the MS-Replication SQL Server source documentation

Thanks,

Mohammed

[john_wang]

Hello Mohammed, @MoeE ,

You’re right — a primary key or unique index is not mandatory for MS-CDC. However, performance can degrade significantly, especially when the target table is large. This is because the target database must locate the correct row for updates, and without a primary key or unique index, this process becomes much less efficient. Defining a primary key or unique index helps speed up row identification and improves overall performance.

Regards,

John.