Migrate on-premises self-managed Oracle to on-premises self-managed PostgreSQL-Data Transmission Service(DTS)-阿里云帮助中心

Prerequisites

The self-managed Oracle database is version 9i, 10g, 11g, 12c, 18c, or 19c.
Ensure that archived logs have a reasonable retention period and are accessible. For more information, see ARCHIVELOG.
Enable supplemental logging for the self-managed Oracle database, including the Supplemental_log_data_pk and Supplemental_log_data_ui options. For more information, see Supplemental Logging.
Tables to be migrated must have a primary key or a UNIQUE NOT NULL index.
You must have a PostgreSQL instance.
Before starting the data migration, review the DTS capabilities and limitations for an Oracle source database. We also recommend using Advanced Database & Application Migration (ADAM) to perform a database evaluation to ensure a smooth migration to the cloud. For more information, see Limitations and preparations for an Oracle database and Database evaluation overview.

Usage notes

Note

During schema migration, DTS migrates the foreign keys from the source database to the destination database.
During full migration and incremental migration, DTS temporarily disables constraint checks and cascaded foreign key operations at the session level. Cascaded update or delete operations in the source database during the migration can cause data inconsistency.

Type	Description
Limits on the source database	Bandwidth requirements: The server that hosts the source database must have sufficient outbound bandwidth. Otherwise, the data migration speed is affected. If the source database is connected over a leased line, you must configure one of the virtual IP addresses (VIPs) in the connection information. This allows the Oracle Real Application Clusters (RAC) to connect to the data migration task over the leased line. If the self-managed Oracle database uses an RAC architecture and is connected over a leased line, VPN Gateway, Smart Access Gateway, Database Gateway (DG), or Cloud Enterprise Network (CEN), or from an ECS instance, you cannot configure a Single Client Access Name (SCAN) IP address. You can only configure one of the VIPs in the connection information. If you use this method, node switching for RAC is not supported. If the data to be migrated contains empty strings of the `varchar2` type, which Oracle treats as null, and the corresponding destination database field has a NOT NULL constraint, the migration task fails. If the FGA (Fine-Grained Audit) policy is enabled on the table to be migrated, DTS cannot recognize the `ORA_ROWSCN` pseudocolumn, which will cause the migration job to fail. Note You can disable the FGA policy for the tables to be migrated, or choose not to migrate data from these tables. Requirements for migration objects: The tables to be migrated must have a primary key or a unique constraint, and the fields must be unique. Otherwise, duplicate data may appear in the destination database. If your self-managed Oracle database is version 12c or later, the names of the tables to be migrated must not exceed 30 bytes in length. If you migrate objects at the table level and need to edit them, such as mapping table or column names, a single data migration task supports a maximum of 1,000 tables. If this limit is exceeded, an error is reported after you submit the task. In this case, split the tables into multiple batches and configure a separate task for each batch, or configure a task to migrate the entire database. For incremental migration, Redo Logs and Archive Logs: Must be enabled. For an incremental data migration task, DTS requires that Redo Logs and Archive Logs in the source database are retained for more than 24 hours. For a task that includes both full and incremental data migration, DTS requires that Redo Logs and Archive Logs are retained for at least 7 days. After the full data migration is complete, you can change the retention period to more than 24 hours. If the retention period is shorter than required, the DTS task may fail because it cannot obtain the logs. In extreme cases, this may cause data inconsistency or loss. Issues caused by a log retention period shorter than the DTS requirement are not covered by the DTS Service-Level Agreement (SLA). Limitations on source database operations: During schema migration and full data migration, do not perform DDL operations that change the database or table schema. Otherwise, the data migration task fails. If you perform only full data migration, do not write new data to the source instance. Otherwise, the source and destination data will be inconsistent. To maintain real-time data consistency, select schema migration, full data migration, and incremental data migration. Updating large text fields separately is not supported and will cause the task to fail.
Other limits	Before migrating data, evaluate the performance of the source and destination databases. Perform data migration during off-peak hours. During full data migration, DTS consumes some read and write resources from the source and destination databases, which may increase the database load. Because full data migration performs concurrent INSERT operations, it causes table fragmentation in the destination database. As a result, the table storage space in the destination database is larger than that in the source instance. DTS attempts to resume failed migration tasks within seven days. Therefore, before you switch your business to the destination instance, you must stop or release the task. Alternatively, use the `revoke` command to revoke the write permissions of the account that DTS uses to access the destination instance. This prevents the source data from overwriting the data in the destination instance if the task is automatically resumed. Ensure that the character sets of the source and destination databases are compatible. Otherwise, data inconsistency or task failure may occur. Use the schema migration feature of DTS. Otherwise, the task may fail due to incompatible data types. The time zones of the source and destination databases must be the same. Migration of foreign tables is not supported. The migration of `PACKAGE`, `PACKAGE_BODY`, `MATERIALIZED_VIEW`, `SYNONYM`, `TYPE`, `TYPE_BODY`, and `PROCEDURE` is not supported. The destination self-managed PostgreSQL database does not support writing the string terminator ('`\0`'). If synchronized data contains this terminator, DTS does not write the terminator to the destination database, which may lead to data inconsistency. When migrating CHECK constraints from a source self-managed Oracle database to a destination self-managed PostgreSQL database, DTS converts them to NOT NULL constraints. You can migrate custom TYPE objects to the destination self-managed PostgreSQL database. However, DTS does not migrate built-in TYPE objects that Oracle automatically generates. During incremental migration, using Oracle Data Pump to import data into the source database is not supported. This may cause data loss. For a full or incremental migration task, if the tables to be migrated in the source database contain foreign keys, triggers, or event triggers, DTS temporarily sets the session_replication_role parameter to replica at the session level if the destination database account is a privileged account or has superuser permissions. If the destination database account does not have these permissions, you must manually set the session_replication_role parameter to replica in the destination database. During this period (when session_replication_role is replica), if cascade update or delete operations occur in the source database, data inconsistency may occur. After the DTS migration task is released, you can change the session_replication_role parameter back to origin. If a task fails, DTS support staff will attempt to restore it within eight hours. During restoration, they may restart the task or adjust its parameters. Note Only DTS task parameters are modified—not database parameters. Parameters that may be adjusted include those listed in Modify instance parameters.

Billing

Migration type	Channel specification fee	Public network traffic fees
Schema migration and full data migration	Free of charge.	DTS charges public network traffic fees when the Access Method for the destination database is set to Public IP Address. For more information, see Billing overview.
Incremental data migration	This is a paid service. For more information, see Billing overview.

Migration types

Migration type	Description
Schema migration	DTS migrates object schemas to the destination PostgreSQL instance. DTS supports the following object types: tables, views, synonyms, triggers, stored procedures, stored functions, packages, and custom types. Note DTS is currently incompatible with triggers. Delete the triggers from the source database to prevent data inconsistency. For more information, see Configure a synchronization or migration task when the source database contains triggers.
Full data migration	DTS migrates all existing data in the objects from the self-managed Oracle database to the destination PostgreSQL instance. Note Before schema migration and full data migration are complete, do not perform DDL operations on the objects. Otherwise, the migration task might fail.
Incremental data migration	After full data migration is complete, DTS polls for and captures redo logs from the source self-managed Oracle database, and synchronizes incremental data updates to the destination PostgreSQL instance. Incremental data migration lets you seamlessly migrate your Oracle database to a PostgreSQL instance with minimal downtime for your self-managed applications.

SQL operations for incremental migration

Type	SQL statement
DML	`INSERT`, `UPDATE`, and `DELETE`
DDL	`CREATE TABLE` Note `CREATE TABLE` is not supported for tables with partitions or subpartitions, tables defined with functions, or `CREATE TABLE AS SELECT` statements. `ALTER TABLE`, including `ADD COLUMN`, `ADD INDEX`, `DROP COLUMN`, `DROP INDEX`, `MODIFY COLUMN`, and `RENAME COLUMN` `DROP TABLE` `RENAME TABLE`, `TRUNCATE TABLE`, and `CREATE INDEX`

Before you begin

Log on to the source self-managed Oracle database to create a database account and grant it the required permissions.

Note

If you have an account with the permissions listed in the following table, you can skip this step.

Database	Schema migration	Full data migration	Incremental data migration
Self-managed Oracle database	Permissions of the schema owner	Permissions of the schema owner	Fine-grained permissions
Self-managed PostgreSQL database	Permissions of the schema owner

For details on creating a database account and granting it permissions, see the following documentation:

For a self-managed Oracle database, see Prepare a database account, CREATE USER, and GRANT.
For a self-managed PostgreSQL database, see the CREATE USER and GRANT syntax.

Important

To migrate incremental data, you must also enable archive logging and supplemental logging. For more information, see database configuration.

Procedure

Navigate to the migration task list page for the destination region using one of the following methods.
From the DTS console
1. Log on to the Data Transmission Service (DTS) console.
2. In the navigation pane on the left, click Data Migration.
3. In the upper-left corner of the page, select the region where the migration instance is located.
From the DMS console

Note
The actual operations may vary based on the mode and layout of the DMS console. For more information, see Simple mode console and Customize the layout and style of the DMS console.
1. Log on to the Data Management (DMS) console.
2. In the top menu bar, choose Data + AI > Data Transmission (DTS) > Data Migration.
3. To the right of Data Migration Tasks, select the region where the migration instance is located.
Click Create Task to navigate to the task configuration page.

Configure the source and destination databases.

Warning

After you select the source and destination instances, we recommend that you carefully read the limits displayed at the top of the page. Otherwise, the task may fail or data inconsistency may occur.

Category	Parameter	Description
N/A	Task Name	DTS automatically generates a task name. We recommend that you specify a descriptive name for easy identification. The name does not need to be unique.
Source Database	Database Type	Select Oracle.
	Connection Type	Select a connection type based on the deployment location of the source database. This topic uses Self-managed Database on ECS as an example. Note If your self-managed database is of a different instance type, you must also complete the required preparations.
	Instance Region	Select the region where the source Oracle database is located.
	ECS Instance ID	Select the ID of the ECS instance that hosts the source Oracle database.
	Port	Enter the service port of the source Oracle database. The default value is 1521.
	Oracle Type	Non-RAC Instance: If you select this option, you must also specify the SID. RAC or PDB Instance: If you select this option, you must also specify the Service Name.
	Database Account	Enter the account for the source Oracle database. For the required permissions, see Preparations.
	Database Password	Enter the password for the database account.
Destination Database	Database Type	Select PostgreSQL.
	Connection Type	Select a connection type based on the deployment location of the destination database. This topic uses Self-managed Database on ECS as an example.
	Instance Region	Select the region where the destination PostgreSQL instance is located.
	ECS Instance ID	Select the ID of the ECS instance that hosts the destination PostgreSQL database.
	Port	Enter the service port of the destination PostgreSQL database. The default value is 3433.
	Database Name	Enter the name of the database in the destination PostgreSQL instance that will receive the migrated objects.
	Database Account	Enter the account for the destination PostgreSQL instance. For the required permissions, see Preparations.
	Database Password	Enter the password for the database account.
	Encryption	Select a connection method. In this example, Non-encrypted is selected. If you need to connect to the database by using SSL encryption, select SSL-encrypted, and then upload the CA Certificate, Client Certificate, and Private Key of Client Certificate as needed. Then, enter the Private Key Password of Client Certificate. Note If you select SSL-encrypted for a self-managed PostgreSQL database, you must upload the CA Certificate. If you need to use a client certificate, you must upload both the Client Certificate and the Private Key of Client Certificate, and then enter the Private Key Password of Client Certificate. For information about the SSL encryption feature for an RDS for PostgreSQL instance, see SSL connection encryption.

After you complete the configuration, click Test Connectivity and Proceed at the bottom of the page.
Note
- Ensure that the IP address segment of the DTS service is automatically or manually added to the security settings of the source and destination databases to allow access from DTS servers. For more information, see Add DTS server IP addresses to a whitelist.
- If the source or destination database is a self-managed database (the Access Method is not Alibaba Cloud Instance), you must also click Test Connectivity in the CIDR Blocks of DTS Servers dialog box that appears.

Configure the task objects.

Parameter	Description
Migration Types	If you only need to perform a full migration, select both Schema Migration and Full Data Migration. To perform a migration with no downtime, select Schema Migration, Full Data Migration, and Incremental Data Migration. Note If you do not select Schema Migration, you must ensure that a database and tables to receive the data exist in the destination database. You can also use the object name mapping feature in the Selected Objects box as needed. If you do not select Incremental Data Migration, do not write new data to the source instance during data migration to ensure data consistency.
Processing Mode for Existing Destination Tables	Precheck and Report Errors: Checks whether tables with the same names exist in the destination database. If no tables with the same names exist, the precheck is passed. If tables with the same names exist, an error is reported during the precheck, and the data migration task does not start. Note If a table in the destination database has the same name but cannot be easily deleted or renamed, you can change the name of the table in the destination database. For more information, see Object name mapping. Ignore Errors and Proceed: Skips the check for tables with the same names. Warning Selecting Ignore Errors and Proceed may cause data inconsistency and business risks. For example: If the table schemas are consistent and a record in the destination database has the same primary key value as a record in the source database: During full migration, DTS keeps the record in the destination database. The record from the source database is not migrated. During incremental migration, DTS does not keep the record in the destination database. The record from the source database overwrites the record in the destination database. If the table schemas are inconsistent, only some columns of data may be migrated, or the migration may fail. Proceed with caution.
Source Objects	In the Source Objects box, click the objects to migrate, and then click to move them to the Selected Objects box.
Selected Objects	To change the name of a single migration object in the target instance, right-click the object in the Selected Objects box. For more information, see Map individual schema, table, and column names. To change the names of multiple migration objects in the target instance, click Selected Objects in the upper-right corner of the Batch Edit box. For more information, see Map multiple schema, table, and column names. Note If you use the object name mapping feature, other objects that depend on the renamed object might fail to migrate. To filter data by using a WHERE clause, right-click the table in the Selected Objects box and specify the filter conditions in the dialog box. For more information, see Set filter conditions. To select the SQL operations for incremental data migration at the database or table level, right-click the migration object in the Selected Objects box and select the desired SQL operations in the dialog box that appears.

Click Next: Advanced Settings to configure advanced parameters.

Parameter	Description
Dedicated Cluster for Task Scheduling	By default, DTS schedules tasks on a shared cluster. You do not need to select one. If you want more stable tasks, you can purchase a dedicated cluster to run DTS migration tasks.
Retry Time for Failed Connections	After the migration task starts, if the connection to the source or destination database fails, DTS reports an error and immediately begins to retry the connection. The default retry duration is 720 minutes. You can customize the retry time to a value from 10 to 1440 minutes. We recommend that you set the duration to more than 30 minutes. If DTS reconnects to the source and destination databases within the specified duration, the migration task automatically resumes. Otherwise, the task fails. Note For multiple DTS instances that share the same source or destination, the network retry time is determined by the setting of the last created task. Because you are charged for the task during the connection retry period, we recommend that you customize the retry time based on your business needs, or release the DTS instance as soon as possible after the source and destination database instances are released.
Retry Time for Other Issues	After the migration task starts, if a non-connectivity issue, such as a DDL or DML execution exception, occurs in the source or destination database, DTS reports an error and immediately begins to retry the operation. The default retry duration is 10 minutes. You can customize the retry time to a value from 1 to 1440 minutes. We recommend that you set the duration to more than 10 minutes. If the related operations succeed within the specified retry duration, the migration task automatically resumes. Otherwise, the task fails. Important The value of Retry Time for Other Issues must be less than the value of Retry Time for Failed Connections.
Enable Throttling for Full Data Migration	During full migration, DTS consumes read and write resources on the source and destination databases, which may increase the database load. If required, you can enable throttling for the full migration task. You can set Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s) to reduce the load on the destination database. Note This configuration item is available only if you select Full Data Migration for Migration Types. You can also adjust the full migration speed after the migration instance is running.
Enable Throttling for Incremental Data Migration	If required, you can also choose to set speed limits for the incremental migration task. You can set RPS of Incremental Data Migration and Data migration speed for incremental migration (MB/s) to reduce the load on the destination database. Note This configuration item is available only if you select Incremental Data Migration for Migration Types. You can also adjust the incremental migration speed after the migration instance is running.
Environment Tag	Optional. Select an environment tag to identify the instance.
Actual Write Code	You can select the encoding type for writing data to the destination based on your requirements.
Configure ETL	Choose whether to enable the extract, transform, and load (ETL) feature. For more information, see What is ETL? Valid values: Yes: Enables the ETL feature. Enter data processing statements in the code editor. For more information, see Configure ETL in a data migration or data synchronization task. No: Disables the ETL feature.
Monitoring and Alerting	Select whether to set alerts and receive alert notifications based on your business needs. No: Does not set an alert. Yes: Configure alerts by setting an alert threshold and an alert contact. If a migration fails or the latency exceeds the threshold, the system sends an alert notification.

Save the task and run a precheck.
- To view the parameters for configuring this instance when you call the API operation, move the pointer over the Next: Save Task Settings and Precheck button and click Preview OpenAPI parameters in the bubble that appears.
- If you do not need to view or have finished viewing the API parameters, click Next: Save Task Settings and Precheck at the bottom of the page.
Note
- Before the migration task starts, DTS performs a precheck. The task starts only after it passes the precheck.
- If the precheck fails, click View Details next to the failed check item, fix the issue based on the prompt, and then run the precheck again.
- If a warning is reported during the precheck:
  
  For check items that cannot be ignored, click View Details next to the failed item, fix the issue based on the prompt, and then run the precheck again.
  
  For check items that can be ignored, you can click Confirm Alert Details, Ignore, OK, and Precheck Again to skip the alert item and run the precheck again. If you choose to ignore a warning, it may cause issues such as data inconsistency and pose risks to your business.

Purchase the instance.

When the Success Rate is 100%, click Next: Purchase Instance.

On the Purchase page, select the link specification for the data migration instance. For more information, see the following table.

Category	Parameter	Description
New Instance Class	Resource Group Settings	Select the resource group to which the instance belongs. The default value is default resource group. For more information, see What is Resource Management?
New Instance Class	Instance Class	DTS provides migration specifications with different performance levels. The link specification affects the migration speed. You can select a specification based on your business scenario. For more information, see Data migration link specifications.

After the configuration is complete, read and select Data Transmission Service (Pay-as-you-go) Service Terms.
Click Buy and Start. In the OK dialog box that appears, click OK.

You can view the progress of the migration task on the Data Migration Tasks list page.
Note
- If the migration task does not include incremental migration, it stops automatically after the full migration is complete. After the task stops, its Status changes to Completed.
- If the migration task includes incremental migration, it does not stop automatically. The incremental migration task continues to run. While the incremental migration task is running, the Status of the task is Running.