MS-CDC DDL operations

[ay3]

TITEL: Contradiction between Official Documentation and Qlik Chatbot regarding MS-CDC DDL Replication

Hello,

I'm experiencing confusion due to contradictory information between the official documentation and Qlik's chatbot regarding DDL replication with MS-CDC source in Qlik Replicate.

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Environment:

• Qlik Replicate: November 2025
• Source: Microsoft SQL Server (MS-CDC)
• Target: Microsoft SQL Server
• "Capture DDL events" option: Enabled
• "Enable MS-CDC on all captured tables" option: Enabled

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The Issue:

1. Official Documentation (Page 364-365):

"Limitations when capturing DDL operations are as follows:

Table-level DDLs are not supported. When a table DDL is encountered, the DDL will be transferred to the target and the table will be suspended to allow the CT table to be manually aligned."

→ Documentation clearly states "not supported" and requires manual intervention

2. Qlik Chatbot Response:

When I asked the same question to Qlik's chatbot:

• "MS-CDC DDL works well"
• "DDL is reflected normally without operator intervention"
• "DML is also reflected normally after DDL"

→ Chatbot claims it works automatically

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Questions:

Q1. What is the actual behavior?

Which is correct - the official documentation or the chatbot?

Scenario:

sql

-- Source MSSQL
ALTER TABLE dbo.Employees ADD Email NVARCHAR(100);
INSERT INTO dbo.Employees (ID, Name, Email) 
VALUES (1, 'John', 'john@example.com');

Case A: If documentation is correct

1. ALTER TABLE detected
2. DDL "transferred to the target"
3. ⚠️ Table SUSPENDED
4. ❌ INSERT not replicated (table suspended)
5. Administrator manually aligns CT table
6. Resume Table executed
7. DML replication resumes afterwards

Case B: If chatbot is correct

1. ALTER TABLE detected
2. ✅ DDL automatically executed on target
3. ✅ Table NOT suspended
4. ✅ INSERT replicated immediately
5. ✅ Everything handled automatically without intervention

Which case reflects the actual behavior?

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Q2. Exact meaning of "DDL will be transferred to the target"

Does this mean:

Option A: DDL is automatically executed on target DB, schema changes automatically Option B: DDL information is only logged/transferred as metadata, administrator must execute manually

Which is correct?

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Q3. Exact meaning of "not supported"

Documentation states "Table-level DDLs are not supported":

Interpretation A: Not automatically replicated, hence "not supported" Interpretation B: Captured but not fully automatic, hence "limited support" Interpretation C: Actually works well (per chatbot) but documentation is outdated

Which is correct?

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Q4. Does SUSPENDED state actually occur?

Q4-1: When "Capture DDL events" is enabled and a table-level DDL occurs, does the table actually enter SUSPENDED state?

Q4-2: If SUSPENDED occurs, is DML replication also halted?

Q4-3: What specific actions must the administrator take before Resume?

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Q5. Supported DDL Scope

The chatbot said it's "reflected normally" - exactly which DDLs are automatically supported?

Full automatic support:

sql

-- Which of these work without operator intervention?
CREATE TABLE dbo.NewTable (...);
ALTER TABLE dbo.Employees ADD Email NVARCHAR(100);
ALTER TABLE dbo.Employees DROP COLUMN TempColumn;
ALTER TABLE dbo.Employees ALTER COLUMN Salary DECIMAL(18,2);
DROP TABLE dbo.OldTable;
TRUNCATE TABLE dbo.TempData;  -- docs say not supported
CREATE INDEX IX_Name ON dbo.Employees(Name);
DROP INDEX IX_Name ON dbo.Employees;

For each DDL, please clarify:

• ✅ Fully automatic (no SUSPENDED)
• ⚠️ Partial support (SUSPENDED → Resume required)
• ❌ Not supported

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Q6. DML Replication Scope

Chatbot said "DML is reflected normally":

Basic DML:

sql

INSERT INTO dbo.Employees (...) VALUES (...);
UPDATE dbo.Employees SET ... WHERE ...;
DELETE FROM dbo.Employees WHERE ...;
MERGE INTO dbo.Employees ...;

Bulk DML:

sql

BULK INSERT dbo.Employees FROM '...';
INSERT INTO dbo.Employees SELECT * FROM dbo.TempTable;  -- docs say not supported
BCP utility;

Special DML:

sql

WRITETEXT ...;  -- docs say not supported
UPDATETEXT ...;  -- docs say not supported
```

Please clarify which are supported.

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### **Q7. CT (Change Table) Manual Alignment**

If SUSPENDED actually occurs:

**Please provide specific recovery process:**
```
Step 1: ???
Step 2: ???
Step 3: Resume Table

Specifically:

• How do you "align" the CT table?
• Do you run SQL queries?
• Do you use Qlik tools?
• Must you manually execute DDL on target?

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Request:

1. Please clarify the discrepancy between documentation and chatbot
2. I need to understand the actual operational behavior
3. If documentation is outdated or incomplete, please update it
4. A detailed DDL/DML support matrix would be greatly appreciated

This information is critical for production environment planning and decision-making.

Thank you.

[pablolabbe]

Official documentation is the single source of truth .Chatbots can provide incorrect answers, so you always have to review it.