Impact on the Source Database
When DTS performs full data synchronization, it consumes certain resources from the source database, which may lead to an increase in the source database's load and put additional pressure on it. If your database configuration is insufficient, it is recommended to perform data migration during off-peak hours.
Impact on the Target Database
During the migration process, DTS will use a system service account to create a table under the TencentDTSData database on the target end, using the task ID (e.g., table name dts-xxxxx). This table is used to record checkpoints, enabling checkpoint restart in case of task interruption.
Migration Architecture
1. Sharded Migration Related Notes:
1.1 Before a sharded cluster is migrated, it is recommended to clean up orphaned documents in the source cluster in advance. Otherwise, data inconsistency issues may arise after migration. For instructions on how to clean up orphaned documents, see the MongoDB official documentation cleanupOrphaned. 1.2 During a sharded migration, do not enable sharding on the source databases and tables being migrated. This is to prevent discrepancies in data distribution between the source and target databases. If sharding is enabled on the source during migration, check the sharding status on the target. If sharding is not enabled on the target, you will need to manually enable it. For detailed instructions on how to enable sharding, see the MongoDB official documentation on Shard a Collection. 1.3 If the source is a TencentDB for MongoDB 3.2 sharded cluster, all shard keys will be treated as hashed shard keys by default during migration. If you want to use range shard keys on the target, create the range shard keys on the target database in advance before the data migration is started.
2. Since a single node does not have an Oplog, incremental migration is not supported when the self-hosted instance is a single node.
Notes
1. Do not perform the following operations during migration, as they may cause the migration task to fail.
Do not modify or delete user information (including usernames, passwords, and permissions) or port numbers in the source or target databases.
Do not perform Oplog clearance operations on the source database.
During the data migration, do not delete the TencentDTSData database on the target database.
2. Be cautious when you operate on the target database during the data migration to avoid data inconsistencies.