|Limits on the source database
- Bandwidth requirements: The server to which the source database belongs must have
sufficient egress bandwidth. Otherwise, the data migration speed is affected.
- The tables to be migrated must have PRIMARY KEY or UNIQUE constraints and all fields
must be unique. Otherwise, the destination database may contain duplicate data records.
- If you select tables as the objects to be migrated and you need to edit tables (such
as renaming tables or columns), up to 1,000 tables can be migrated in a single data
migration task. If you run a task to migrate more than 1,000 tables, a request error
occurs. In this case, we recommend that you split the tables to be migrated, configure
multiple tasks to migrate the tables, or configure a task to migrate the entire database.
- Limits on operations:
- During schema migration and full data migration, do not perform data definition language
(DDL) operations to change the schemas of databases or tables. Otherwise, the data
migration task fails.
- In this scenario, DTS does not support incremental data migration. To ensure data
consistency, we recommend that you do not write data to the source instance during
- In this scenario, DTS supports only schema migration and full data migration. DTS
does not support incremental data migration.
- The characters in the source objects can only be alphanumeric (a to z, A to Z, and
0 to 9). If an object contains other types of characters, schema migration fails.
- AnalyticDB for MySQL has limits on the usage of disk space. If the disk space usage of the nodes in an
AnalyticDB for MySQL cluster reaches 80%, the performance of data writing to the destination database
is compromised and the DTS task is delayed. If the usage reaches 90%, data cannot
be written to the destination database and error messages are returned. We recommend
that you estimate the required disk space based on the objects that you want to migrate.
You must make sure that the destination cluster has sufficient storage space.
- Before you migrate data, evaluate the impact of data migration on the performance
of the source and destination databases. We recommend that you migrate data during
off-peak hours. During full data migration, DTS uses read and write resources of the
source and destination databases. This may increase the loads of the database servers.
- During full data migration, concurrent INSERT operations cause fragmentation in the
tables of the destination database. After full data migration is completed, the tablespace
of the destination database is larger than that of the source database.
- DTS attempts to resume data migration tasks that failed within the last seven days.
Before you switch workloads to the destination cluster, stop or release the data migration
task. You can also run the
revoke command to revoke the write permissions from the accounts that are used by DTS to
access the destination cluster. Otherwise, the data in the source database will overwrite
the data in the destination cluster after the task is resumed.