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If you’ve noticed a delay when restarting your data migration task, it’s probably caused by the source latency in capturing changes. This often happens when you stop a task for a long period, such as overnight, and then restart it. When the task is stopped, it records the last position in the transaction log from which it was reading. When you restart the task, it tries to continue reading from that same point. But if a lot of changes have built up during the downtime, the system needs to process all these accumulated changes first. This backlog can lead to increased latency until all the changes are caught up.
To fix this issue, here are some simple steps you can follow to improve your setup:
First, make sure your replication instance has enough resources. Check that your CPU, memory, and disk I/O are sufficient. Monitoring tools like CloudWatch can show you important metrics such as available memory and CPU usage. If you see these resources are maxed out, consider upgrading your instance.
Next, look at your network connection. Ensure the bandwidth between your source database and the replication instance can handle the volume of changes. Fast read and write speeds help reduce the backlog.
You should also review your task settings. Enabling options like BatchApplyEnabled can improve performance if your endpoint supports it. Double-check your settings to turn off any unnecessary features that may slow down processing.
Additionally, pay attention to your system’s swap file usage. If swap files on your instance grow beyond 1 GB, it can cause reading pauses. Adjusting settings like MemoryLimitTotal, MemoryKeepTime, and StatementCacheSize can help reduce swap file size and improve overall speed.
Finally, consider the timing of your restarts. It may be helpful to restart tasks during periods of low activity or immediately after your database is online again. This approach minimizes the amount of change backlog that needs to be processed at once.
Remember, the main reason for delays is that the system has to process all the changes that accumulated during the downtime, which can take some time depending on how much data has changed. By optimizing resources, network, settings, and restart timing, you can reduce these delays and keep your data migration running smoothly.
For more detailed guidance, you can check out AWS’s troubleshooting resources on latency issues and performance errors.





