This topic describes the precautions and limits when you migrate data from an Oracle database. To ensure that your data migration task runs as expected, read the precautions and limits before you configure the task.

Scenarios of migrating data from an Oracle database

You can view the precautions and limits based on the following migration scenarios:

Migrate data from a self-managed Oracle database to a PolarDB O Edition cluster

The following table describes the precautions and limits.
Category Description
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.
  • If the self-managed Oracle database is deployed in a Real Application Cluster (RAC) architecture and is connected to DTS over an Alibaba Cloud virtual private cloud (VPC), you must connect the Single Client Access Name (SCAN) IP address of the Oracle RAC and the virtual IP address (VIP) of each node to the VPC and configure routes. The settings ensure that your DTS task can run as expected. For more information, see Connect an on-premises database to Alibaba Cloud and Configure a route between DTS and Express Connect, VPN Gateway, or Smart Access Gateway.
    Notice When you configure the source Oracle database in the DTS console, you must enter the SCAN IP address of the Oracle RAC in the Database Endpoint or IP Address field.
  • Requirements for the objects to be migrated:
    • 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 the version of your Oracle database is 12c or later, the names of the tables to be migrated cannot exceed 30 bytes in length.
    • If you select tables as the objects to be migrated and you need to edit tables (such as rename 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 call DTS API operations to configure tasks.
  • If you want to migrate incremental data, you must make sure that the following requirements are met:
    • The data logging feature must be enabled.
    • Data logs are retained for at least 7 days during full data migration. You can wait until full data migration is complete, and then clear the data logs generated in the source database after the DTS task is run.
      Note To ensure data security, DTS stores only 50 GB of data logs or the data logs for the last 24 hours. If the limit is exceeded, DTS automatically clears the cached logs.
      Warning If you clear the data logs of the source database during full data migration, the task may fail to migrate incremental data. For example, full data migration takes more than 24 hours due to the large data volume in the source database and abnormal writing in the destination database. In this case, if the data logs of the source database are cleared during full data migration, DTS cannot obtain the data logs generated 24 hours ago. Therefore, the data migration task may fail.
  • 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.
    • If you perform only full data migration, do not write data to the source database during data migration. Otherwise, data will be inconsistent between the source and destination databases. To ensure data consistency, we recommend that you select Schema Migration, Full Data Migration, and Incremental Data Migration as the migration types.
Other limits
  • 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 complete, 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 instance, 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 instance. Otherwise, the data in the source database will overwrite the data in the destination instance after the task is resumed.

Migrate data from a self-managed Oracle database to a MySQL database

The following table describes the precautions and limits when you migrate data to a MySQL database, such as a self-managed MySQL database and an ApsaraDB RDS for MySQL database.
Category Description
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.
  • If the self-managed Oracle database is deployed in a Real Application Cluster (RAC) architecture and is connected to DTS over an Alibaba Cloud virtual private cloud (VPC), you must connect the Single Client Access Name (SCAN) IP address of the Oracle RAC and the virtual IP address (VIP) of each node to the VPC and configure routes. The settings ensure that your DTS task can run as expected. For more information, see Connect an on-premises database to Alibaba Cloud and Configure a route between DTS and Express Connect, VPN Gateway, or Smart Access Gateway.
    Notice When you configure the source Oracle database in the DTS console, you must enter the SCAN IP address of the Oracle RAC in the Database Endpoint or IP Address field.
  • Requirements for the objects to be migrated:
    • 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 the version of your Oracle database is 12c or later, the names of the tables to be migrated cannot exceed 30 bytes in length.
    • If you select tables as the objects to be migrated and you need to edit tables (such as rename 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 call DTS API operations to configure tasks.
  • If you want to migrate incremental data, you must make sure that the following requirements are met:
    • The data logging feature must be enabled.
    • Data logs are retained for at least 7 days during full data migration. You can wait until full data migration is complete, and then clear the data logs generated in the source database after the DTS task is run.
      Note To ensure data security, DTS stores only 50 GB of data logs or the data logs for the last 24 hours. If the limit is exceeded, DTS automatically clears the cached logs.
      Warning If you clear the data logs of the source database during full data migration, the task may fail to migrate incremental data. For example, full data migration takes more than 24 hours due to the large data volume in the source database and abnormal writing in the destination database. In this case, if the data logs of the source database are cleared during full data migration, DTS cannot obtain the data logs generated 24 hours ago. Therefore, the data migration task may fail.
  • 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.
    • If you perform only full data migration, do not write data to the source database during data migration. Otherwise, data will be inconsistent between the source and destination databases. To ensure data consistency, we recommend that you select Schema Migration, Full Data Migration, and Incremental Data Migration as the migration types.
Other limits
  • 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 complete, 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 instance, 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 instance. Otherwise, the data in the source database will overwrite the data in the destination instance after the task is resumed.
Special cases
  • If the destination database runs on an ApsaraDB RDS for MySQL instance, take note of the following limits:
    • Table names in the ApsaraDB RDS for MySQL instance are case-insensitive. If a table name in the source Oracle database contains uppercase letters, ApsaraDB RDS for MySQL converts all uppercase letters to lowercase letters before creating the table.

      If the source Oracle database contains identical table names that differ only in capitalization, these table names are identified as duplicate. During schema migration, the following message is returned: "The object already exists". To prevent name conflicts in the destination database, you can use the object name mapping feature to capitalize the table names. For more information, see Object name mapping.

    • DTS automatically creates a destination database in the ApsaraDB RDS for MySQL instance. However, if the name of the source database is invalid, you must manually create a database in the ApsaraDB RDS for MySQL instance before you configure the data migration task. For more information, see Create a database on an ApsaraDB RDS for MySQL instance.

Migrate data from a self-managed Oracle database to a PolarDB for MySQL cluster

The following table describes the precautions and limits when you migrate data from a self-managed Oracle database to a PolarDB for MySQL cluster.
Category Description
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.
  • If the self-managed Oracle database is deployed in a Real Application Cluster (RAC) architecture and is connected to DTS over an Alibaba Cloud virtual private cloud (VPC), you must connect the Single Client Access Name (SCAN) IP address of the Oracle RAC and the virtual IP address (VIP) of each node to the VPC and configure routes. The settings ensure that your DTS task can run as expected. For more information, see Connect an on-premises database to Alibaba Cloud and Configure a route between DTS and Express Connect, VPN Gateway, or Smart Access Gateway.
    Notice When you configure the source Oracle database in the DTS console, you must enter the SCAN IP address of the Oracle RAC in the Database Endpoint or IP Address field.
  • Requirements for the objects to be migrated:
    • 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 the version of your Oracle database is 12c or later, the names of the tables to be migrated cannot exceed 30 bytes in length.
    • If you select tables as the objects to be migrated and you need to edit tables (such as rename 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 call DTS API operations to configure tasks.
  • If you want to migrate incremental data, you must make sure that the following requirements are met:
    • The data logging feature must be enabled.
    • Data logs are retained for at least 7 days during full data migration. You can wait until full data migration is complete, and then clear the data logs generated in the source database after the DTS task is run.
      Note To ensure data security, DTS stores only 50 GB of data logs or the data logs for the last 24 hours. If the limit is exceeded, DTS automatically clears the cached logs.
      Warning If you clear the data logs of the source database during full data migration, the task may fail to migrate incremental data. For example, full data migration takes more than 24 hours due to the large data volume in the source database and abnormal writing in the destination database. In this case, if the data logs of the source database are cleared during full data migration, DTS cannot obtain the data logs generated 24 hours ago. Therefore, the data migration task may fail.
  • 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.
    • If you perform only full data migration, do not write data to the source database during data migration. Otherwise, data will be inconsistent between the source and destination databases. To ensure data consistency, we recommend that you select Schema Migration, Full Data Migration, and Incremental Data Migration as the migration types.
Other limits
  • 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 complete, 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 instance, 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 instance. Otherwise, the data in the source database will overwrite the data in the destination instance after the task is resumed.
Special cases If the destination database runs on a PolarDB for MySQL cluster, take note of the following limits:
  • Table names in the PolarDB for MySQL cluster are case-insensitive. If a table name in the source Oracle database contains uppercase letters, PolarDB for MySQL converts all uppercase letters to lowercase letters before creating the table.

    If the source Oracle database contains identical table names that differ only in capitalization, these table names are identified as duplicate. During schema migration, the following message is returned: "The object already exists." To prevent name conflicts in the destination database, you can use the object name mapping feature to capitalize the table names. For more information, see Object name mapping.

  • DTS automatically creates a destination database in the PolarDB for MySQL cluster. However, if the name of the source database is invalid, you must manually create a database in the PolarDB for MySQL cluster before you configure the data migration task. For more information, see Manage databases.

Migrate data from a self-managed Oracle database to an AnalyticDB for PostgreSQL instance

The following table describes the precautions and limits when you migrate data from a self-managed Oracle database to an AnalyticDB for PostgreSQL instance.
Category Description
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.
  • If the self-managed Oracle database is deployed in a Real Application Cluster (RAC) architecture and is connected to DTS over an Alibaba Cloud virtual private cloud (VPC), you must connect the Single Client Access Name (SCAN) IP address of the Oracle RAC and the virtual IP address (VIP) of each node to the VPC and configure routes. The settings ensure that your DTS task can run as expected. For more information, see Connect an on-premises database to Alibaba Cloud and Configure a route between DTS and Express Connect, VPN Gateway, or Smart Access Gateway.
    Notice When you configure the source Oracle database in the DTS console, you must enter the SCAN IP address of the Oracle RAC in the Database Endpoint or IP Address field.
  • Requirements for the objects to be migrated:
    • 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 the version of your Oracle database is 12c or later, the names of the tables to be migrated cannot exceed 30 bytes in length.
    • If you select tables as the objects to be migrated and you need to edit tables (such as rename 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 call DTS API operations to configure tasks.
  • If you want to migrate incremental data, you must make sure that the following requirements are met:
    • The data logging feature must be enabled.
    • Data logs are retained for at least 7 days during full data migration. You can wait until full data migration is complete, and then clear the data logs generated in the source database after the DTS task is run.
      Note To ensure data security, DTS stores only 50 GB of data logs or the data logs for the last 24 hours. If the limit is exceeded, DTS automatically clears the cached logs.
      Warning If you clear the data logs of the source database during full data migration, the task may fail to migrate incremental data. For example, full data migration takes more than 24 hours due to the large data volume in the source database and abnormal writing in the destination database. In this case, if the data logs of the source database are cleared during full data migration, DTS cannot obtain the data logs generated 24 hours ago. Therefore, the data migration task may fail.
  • 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.
    • If you perform only full data migration, do not write data to the source database during data migration. Otherwise, data will be inconsistent between the source and destination databases. To ensure data consistency, we recommend that you select Schema Migration, Full Data Migration, and Incremental Data Migration as the migration types.
Other limits
  • 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 complete, 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 instance, 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 instance. Otherwise, the data in the source database will overwrite the data in the destination instance after the task is resumed.

Migrate data from a self-managed Oracle database to a Kafka cluster

The following table describes the precautions and limits when you migrate data to a Kafka cluster, such as a Message Queue for Apache Kafka instance or a self-managed Kafka cluster.
Category Description
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.
  • If the self-managed Oracle database is deployed in a Real Application Cluster (RAC) architecture and is connected to DTS over an Alibaba Cloud virtual private cloud (VPC), you must connect the Single Client Access Name (SCAN) IP address of the Oracle RAC and the virtual IP address (VIP) of each node to the VPC and configure routes. The settings ensure that your DTS task can run as expected. For more information, see Connect an on-premises database to Alibaba Cloud and Configure a route between DTS and Express Connect, VPN Gateway, or Smart Access Gateway.
    Notice When you configure the source Oracle database in the DTS console, you must enter the SCAN IP address of the Oracle RAC in the Database Endpoint or IP Address field.
  • Requirements for the objects to be migrated:
    • 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 the version of your Oracle database is 12c or later, the names of the tables to be migrated cannot exceed 30 bytes in length.
    • If you select tables as the objects to be migrated and you need to edit tables (such as rename 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 call DTS API operations to configure tasks.
  • If you want to migrate incremental data, you must make sure that the following requirements are met:
    • The data logging feature must be enabled.
    • Data logs are retained for at least 7 days during full data migration. You can wait until full data migration is complete, and then clear the data logs generated in the source database after the DTS task is run.
      Note To ensure data security, DTS stores only 50 GB of data logs or the data logs for the last 24 hours. If the limit is exceeded, DTS automatically clears the cached logs.
      Warning If you clear the data logs of the source database during full data migration, the task may fail to migrate incremental data. For example, full data migration takes more than 24 hours due to the large data volume in the source database and abnormal writing in the destination database. In this case, if the data logs of the source database are cleared during full data migration, DTS cannot obtain the data logs generated 24 hours ago. Therefore, the data migration task may fail.
  • 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.
    • If you perform only full data migration, do not write data to the source database during data migration. Otherwise, data will be inconsistent between the source and destination databases. To ensure data consistency, we recommend that you select Schema Migration, Full Data Migration, and Incremental Data Migration as the migration types.
Other limits
  • 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 complete, 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 instance, 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 instance. Otherwise, the data in the source database will overwrite the data in the destination instance after the task is resumed.

Migrate data between self-managed Oracle databases

The following table describes the precautions and limits when you migrate data between self-managed Oracle databases.
Category Description
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.
  • If the self-managed Oracle database is deployed in a Real Application Cluster (RAC) architecture and is connected to DTS over an Alibaba Cloud virtual private cloud (VPC), you must connect the Single Client Access Name (SCAN) IP address of the Oracle RAC and the virtual IP address (VIP) of each node to the VPC and configure routes. The settings ensure that your DTS task can run as expected. For more information, see Connect an on-premises database to Alibaba Cloud and Configure a route between DTS and Express Connect, VPN Gateway, or Smart Access Gateway.
    Notice When you configure the source Oracle database in the DTS console, you must enter the SCAN IP address of the Oracle RAC in the Database Endpoint or IP Address field.
  • Requirements for the objects to be migrated:
    • 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 the version of your Oracle database is 12c or later, the names of the tables to be migrated cannot exceed 30 bytes in length.
    • If you select tables as the objects to be migrated and you need to edit tables (such as rename 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 call DTS API operations to configure tasks.
  • If you want to migrate incremental data, you must make sure that the following requirements are met:
    • The data logging feature must be enabled.
    • Data logs are retained for at least 7 days during full data migration. You can wait until full data migration is complete, and then clear the data logs generated in the source database after the DTS task is run.
      Note To ensure data security, DTS stores only 50 GB of data logs or the data logs for the last 24 hours. If the limit is exceeded, DTS automatically clears the cached logs.
      Warning If you clear the data logs of the source database during full data migration, the task may fail to migrate incremental data. For example, full data migration takes more than 24 hours due to the large data volume in the source database and abnormal writing in the destination database. In this case, if the data logs of the source database are cleared during full data migration, DTS cannot obtain the data logs generated 24 hours ago. Therefore, the data migration task may fail.
  • 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.
    • If you perform only full data migration, do not write data to the source database during data migration. Otherwise, data will be inconsistent between the source and destination databases. To ensure data consistency, we recommend that you select Schema Migration, Full Data Migration, and Incremental Data Migration as the migration types.
Other limits
  • 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 complete, 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 instance, 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 instance. Otherwise, the data in the source database will overwrite the data in the destination instance after the task is resumed.