migrate-from-mysql-using-aws-dms: fix "test" mislabeled as a system database

tidb-cloud/migrate-from-mysql-using-aws-dms.md

@@ -19,7 +19,7 @@ Before you start the migration, make sure you have read the following:
 
 - If the source database is Amazon RDS or Amazon Aurora, you need to set the `binlog_format` parameter to `ROW`. If the database uses the default parameter group, the `binlog_format` parameter is `MIXED` by default and cannot be modified. In this case, you need to [create a new parameter group](https://docs.aws.amazon.com/dms/latest/userguide/CHAP_GettingStarted.Prerequisites.html#CHAP_GettingStarted.Prerequisites.params), for example `newset`, and set its `binlog_format` to `ROW`. Then, [modify the default parameter group](https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_WorkingWithDBInstanceParamGroups.html#USER_WorkingWithParamGroups.Modifying) to `newset`. Note that modifying the parameter group will restart the database.
 - Check and ensure that the source database uses collations that are compatible with TiDB. The default collation for the utf8mb4 character set in TiDB is `utf8mb4_bin`. But in MySQL 8.0, the default collation is `utf8mb4_0900_ai_ci`. If the upstream MySQL uses the default collation, because TiDB is not compatible with `utf8mb4_0900_ai_ci`, AWS DMS cannot create the target tables in TiDB and cannot migrate the data. To resolve this problem, you need to modify the collation of the source database to `utf8mb4_bin` before the migration. For a complete list of TiDB supported character sets and collations, see [Character Set and Collation](https://docs.pingcap.com/tidb/stable/character-set-and-collation).
-- TiDB contains the following system databases by default: `INFORMATION_SCHEMA`, `PERFORMANCE_SCHEMA`, `mysql`, `sys`, and `test`. When you create an AWS DMS migration task, you need to filter out these system databases instead of using the default `%` to select the migration object. Otherwise, AWS DMS will try to migrate these system databases from the source database to the target TiDB, which will cause the task to fail. To avoid this issue, it is recommended to fill in the specific database and table names.
+When you create an AWS DMS migration task, do not use the default `%` wildcard to select databases. Instead, explicitly specify only the databases and tables that you want to migrate. Otherwise, AWS DMS might attempt to migrate system databases such as `INFORMATION_SCHEMA`, `PERFORMANCE_SCHEMA`, `mysql`, and `sys` from the source MySQL database to TiDB, which can cause the migration task to fail.
 - Add the public and private network IP addresses of AWS DMS to the IP access lists of both source and target databases. Otherwise, the network connection might fail in some scenarios.
 - Use [VPC Peerings](/tidb-cloud/set-up-vpc-peering-connections.md#set-up-vpc-peering-on-aws) or [Private Endpoint connections](/tidb-cloud/set-up-private-endpoint-connections.md) to connect AWS DMS and the TiDB cluster.
 - It is recommended to use the same region for AWS DMS and the TiDB cluster to get better data writing performance.