Will DMS task have any impact on the source database?
I am exploring DMS and am not sure if the tasks will have any impact on the source database
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AWS DMS uses some resources on your source database. During a full load task, AWS DMS performs a full table scan of the source table for each table processed in parallel. Also, each task that you create as part of a migration queries the source for changes as part of the CDC process. For AWS DMS to perform CDC for some sources, such as Oracle, you might need to increase the amount of data written to your database's change log.
If you find that you're overburdening your source database, reduce the number of tasks or tables for each task for your migration. Each task gets source changes independently, so consolidating tasks can decrease the change capture workload.
While AWS Database Migration Service (DMS) is designed to be minimally intrusive, it can have some impact on the source database, particularly during ongoing replication (Change Data Capture or CDC) tasks. Here are a few key points to consider:
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Resource utilization: DMS needs to read from the source database's transaction logs or similar mechanisms to capture changes. This can lead to some additional I/O and CPU usage on the source system.
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Database configuration: Depending on the source database engine, you may need to make some configuration changes. For example:
- For Oracle, DMS uses either LogMiner or binary reader to read redo logs.
- SQL Server requires MS-Replication or MS-CDC to be enabled, which writes additional information to the transaction log.
- MySQL needs row-based binary logging to be enabled.
- PostgreSQL requires setting up logical replication slots.
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Storage requirements: For ongoing replication, the source database needs to retain transaction logs long enough for DMS to process them. This may increase storage requirements, especially for high-volume transactional systems.
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Performance: In most cases, the impact on the source database's performance is minimal. However, during peak times or for very busy systems, you might notice a slight increase in resource usage.
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Permissions: DMS requires certain permissions on the source database, which may necessitate creating a new user account with appropriate access levels.
To minimize any potential impact:
- Schedule initial full load operations during off-peak hours if possible.
- Monitor your source database's performance during the migration process.
- Ensure your source system has adequate resources to handle both normal operations and the additional DMS workload.
- Test the migration process in a non-production environment first to assess the impact on your specific database setup.
While DMS is designed to be efficient, it's important to carefully plan and monitor your migration to ensure it doesn't negatively affect your source database's performance or stability.
Sources
Creating tasks for ongoing replication using AWS DMS - AWS Database Migration Service
Insights into AWS DMS resiliency and recovery scenarios with mitigations – Part 1 | AWS Database Blog
Monitoring AWS DMS tasks - AWS Database Migration Service
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