DMS Migration Task(only CDC) for Ongoing Replication Type, Migration progress struck at 0%

That issue can occur due to various reasons.

1. CDC Load Balancing: AWS DMS uses a load balancing mechanism for Change Data Capture (CDC) tasks to distribute the load across multiple threads. If the source database doesn't generate enough change events initially, the progress might show as 0% until enough changes accumulate. Stopping and resuming the task can trigger the load balancing mechanism and start the replication process.

2. Table Metadata Retrieval: Before starting the CDC replication, DMS retrieves the table metadata from the source and target databases. If there are a large number of tables or complex table structures, this process can take some time, during which the migration progress might show as 0%.

3. Triggers on Target Tables: As you mentioned, triggers on the target tables can potentially cause issues with the CDC replication process. DMS might need to perform additional checks or handling when dealing with triggers, which could delay the migration progress from updating initially.

4. Large Transaction Logs: If the source database has a significant amount of transaction logs or change events to process initially, DMS might take some time to catch up and start showing progress. This delay could be more pronounced if there are also other factors like complex table structures or a large number of tables.

5. Network Latency: High network latency between the DMS replication instance and the source or target databases can sometimes cause delays in the progress updating. This is more likely to occur in cross-region or cross-account setups.

6. Database Load: If the source or target databases are under heavy load, it might impact the CDC replication process and cause delays in the progress updating initially.

To mitigate these issues, you can try the following:

1. Increase CDC Max Batch Size: You can increase the maxBatchSize parameter in the DMS task settings to allow DMS to process larger batches of changes, which might help in scenarios with high change volume or large transaction logs.

2. Use Parallel Load Threads: If you have a large number of tables, consider increasing the number of parallel load threads in the DMS task settings to speed up the initial metadata retrieval process.

3. Optimize Triggers: Review and optimize any triggers on the target tables to minimize their impact on the CDC replication process.

4. Monitor Database Load: Monitor the source and target database loads during the CDC replication process and consider adjusting resources or scheduling the migration during off-peak hours if necessary.

5. Check Network Latency: If you're experiencing high network latency, consider moving the DMS replication instance closer to the source and target databases or optimizing the network connectivity.