Help Center/ Data Replication Service/ Real-Time Synchronization/ Between Self-built Databases/ From DB2 for LUW to GaussDB Distributed
Updated on 2024-09-25 GMT+08:00
View PDF
Share

From DB2 for LUW to GaussDB Distributed

Supported Source and Destination Databases

Table 1 Supported databases

Source DB

Destination DB

DB2 for LUW 9.7, 10.1, 10.5, 11.1, and 11.5

GaussDB distributed

Precautions

Before creating a synchronization task, read the restrictions listed in the following table.

  • You are advised to create an independent database account for DRS task connection to prevent task failures caused by database account password modification.
  • After changing the account passwords for the source and destination databases, modify the connection information of the DRS task by referring to Modifying Connection Information to prevent automatic retry after a task failure. Automatic retry will lock the database accounts.
Table 2 Precautions

Type

Restrictions

Database permissions
  • Source database
    • To perform full synchronization, the CONNECT and DATAACCESS permissions are required.
    • To perform full+incremental synchronization, the DBADM permission is required.
    • If you select full+incremental synchronization, ensure that the archive log of the source database is enabled and the Datacapture attribute of the table to be synchronized is Y.
  • Destination database
    • Database-level permission: Log in to the postgres base database as user root or other DATABASE users with the sysadmin role, and grant the CREATE and CONNECT permissions to user DATABASE.
    • Schema-level permission: Log in to the database as user root or user DATABASE with the sysadmin role, or the owner of the database, and grant the CREATE and USAGE permissions of the schema to the user.
    • Table-level permission: Log in to the database as user root or user DATABASE with the sysadmin role, or the owner of the database, and grant the SELECT, UPDATE, INSERT, and DELETE permissions for all tables in the SCHEMA to the user.
    • If gs_loader is used to create system catalogs (such as public.pgxc_copy_error_log and public.gs_copy_summary) in the destination database, the all privilege permission is required for accessing the system catalogs.For details, see gs_loader.

Synchronization object
  • During full synchronization, tables, common indexes, primary key and unique constraints, and data can be synchronized. Tables can be synchronized in real time during incremental synchronization.
  • User-defined types are not supported.
  • The maximum precision supported by the TIMESTAMP type is 6.
  • During full synchronization, the table structure does not support bitmap indexes, inverted indexes, function indexes, and XML indexes.
  • The LOB type supported by incremental synchronization cannot exceed 10 MB.
  • VARCHAR or VARGRAPHIC data whose length exceeds 3998 characters cannot be synchronized during the incremental synchronization.
  • Tables whose default values contain expression functions cannot be synchronized.
  • Temporary tables in the source database cannot be synchronized.
  • DDL statements executed in the source database cannot be synchronized.
  • For a full+incremental task, tables without primary keys that contain XML fields cannot be synchronized.
  • If a floating point number is used as the primary key, incremental synchronization may cause data inconsistency.

Source database
  • Database object names, such as the database name and table name, support English characters and symbols such as #, $, and _. DRS does not support non-ASCII characters or special characters .>`<'\,|?!" Object names will be converted to lowercase letters after being synchronized to the destination database. To avoid synchronization failures, ensure that the selected source database tables do not contain tables with the same name but different letter cases.
  • Only the GBK and UTF8 character sets can be synchronized.

Destination database
  • The destination database must be a GaussDB distributed instance.
  • Ensure that a database named in lowercase letters has been created in destination database.
  • Do not use foreign keys for tables during synchronization. Otherwise, the sequence of writing data to different tables may be inconsistent with that in the source database, which may trigger foreign key constraints and cause synchronization failures.
  • The destination table can contain more columns than the source table. However, the following failures must be avoided:

    Assume that extra columns on the destination cannot be null or have default values. If newly inserted data records are synchronized from the source to the destination, the extra columns will become null, which does not meet the requirements of the destination and will cause the task to fail.

    Assume that extra columns on the destination must be fixed at a default value and have a unique constraint. If newly inserted data records are synchronized from the source to the destination, the extra columns will contain multiple default values. That does not meet the unique constraint of the destination and will cause the task to fail.

Precautions
  • Do not use an imprecise value type as the primary key in the database because the synchronization of UPDATE and DELETE statements in the DRS incremental scenario will be affected.
  • Arm VMs are not supported.
  • If a table that does not have a primary key contains LOB or LONG data types, data may be inconsistent during incremental synchronization.
  • If the character sets of the source database are different from those of the destination database, adjust the field length of the destination database based on the site requirements. For example, the source character set is GBK and the destination character set is UTF8, a Chinese character of GBK occupies two bytes, and a Chinese character of UTF8 occupies three bytes. When CHAR or VARCHAR data type is synchronized to the destination database, the field length may exceed the defined length, so you need to increase the field length to 1.5 times of that in the source database.
  • Before starting a full+incremental task, ensure that the source database dose not contain uncommitted transactions. You are advised to stop writing data to the source database and then start the task.
  • After a task is started, the detach operation on a partition table may cause data inconsistency.
  • During synchronization, do not modify or delete the usernames, passwords, permissions, or ports of the source and destination databases.
  • During the synchronization, the source database cannot contain uncommitted DDL transactions.
  • Full synchronization consists of two phases: table structure synchronization (including indexes) and real-time synchronization. If the structure of a table is created in the destination database, real-time synchronization starts. If a table fails to be synchronized, you can restart the task to synchronize the table data. However, the table structure is not synchronized, so you must manually create the table in the destination database.
  • When the structure of a partitioned table is synchronized during a full synchronization, the partitioned table is converted to a non-partitioned table.
  • During the full synchronization of table structures, only default value constraints of the character string or number type are supported. Default value constraints of the function or sequence type are not supported. If necessary, create default value constraints for the corresponding table in the destination database.
  • During table structure synchronization in the full phase, if there is a schema with the same name as a user in the destination database and another user is used to synchronize the table structure to the schema, run the grant [role] to [role] command to grant permissions to the user. Otherwise, the synchronization may fail because the table structure cannot be created.
  • Do not write data to the destination database table during full synchronization. Otherwise, data will be inconsistent.
  • During an incremental synchronization, 0x00 at the end of BLOB and the spaces at the end of CLOB are truncated.
  • You can add additional objects in the incremental synchronization phase.
  • During an incremental synchronization, if you update the primary key column or the first column of a table that does not have a primary key in the source database DB2 for LUW, the distribution column will be updated in the GaussDB database, which may cause data inconsistency. Thus, do not update the preceding columns.

Procedure

  1. On the Data Synchronization Management page, click Create Synchronization Task.
  2. On the Create Synchronization Instance page, select a region and project, specify the task name, description, and the synchronization instance details, and click Create Now.

    • Task information description
      Figure 1 Synchronization task information
      Table 3 Task information

      Parameter

      Description

      Region

      The region where the replication instance is deployed. You can change the region.

      Project

      The project corresponds to the current region and can be changed.

      Task Name

      The task name must start with a letter and consist of 4 to 50 characters. It can contain only letters, digits, hyphens (-), and underscores (_).

      Description

      The description consists of a maximum of 256 characters and cannot contain special characters !=<>'&"\
    • Synchronization instance details
      Figure 2 Synchronization instance details
      Table 4 Synchronization instance settings

      Parameter

      Description

      Data Flow

      Choose Self-built to self-built.

      Source DB Engine

      Select DB2 for LUW.

      Destination DB Engine

      Select GaussDB Distributed.

      Network Type

      Public network is used as an example. Available options: Public network and VPN or Direct Connect

      VPC

      Select an available VPC.

      Synchronization Instance Subnet

      Select the subnet where the synchronization instance is located. You can also click View Subnets to go to the network console to view the subnet where the instance resides.

      By default, the DRS instance and the destination DB instance are in the same subnet. You need to select the subnet where the DRS instance resides, and there are available IP addresses for the subnet. To ensure that the synchronization instance is successfully created, only subnets with DHCP enabled are displayed.

      Security Group

      Select a security group. You can use security group rules to allow or deny access to the instance.

      Synchronization Mode
      • Full+Incremental

        This synchronization mode allows you to synchronize data in real time. After a full synchronization initializes the destination database, an incremental synchronization parses logs to ensure data consistency between the source and destination databases.

      • Full

        All objects and data in non-system databases are synchronized to the destination database at a time. This mode is applicable to scenarios where service interruption is acceptable.

      Specify EIP

      This parameter is available when you select Public network for Network Type. Select an EIP to be bound to the DRS instance. DRS will automatically bind the specified EIP to the DRS instance and unbind the EIP after the task is complete. The number of specified EIPs must be the consistent with that of DB instances.

      For details about the data transfer fee generated using a public network, see EIP Price Calculator.
    • AZ
      Figure 3 AZ
      Table 5 Task AZ

      Parameter

      Description

      AZ

      Select the AZ where you want to create the DRS task. Selecting the one housing the source or destination database can provide better performance.
    • Enterprise Project and Tags
      Figure 4 Enterprise projects and tags
      Table 6 Enterprise Project and Tags

      Parameter

      Description

      Enterprise Project

      An enterprise project you would like to use to centrally manage your cloud resources and members. Select an enterprise project from the drop-down list. The default project is default.

      For more information about enterprise project, see Enterprise Management User Guide.

      To customize an enterprise project, click Enterprise in the upper right corner of the console. The Enterprise Project Management Service page is displayed. For details, see Creating an Enterprise Project in Enterprise Management User Guide.

      Tags
      • Tags a task. This configuration is optional. Adding tags helps you better identify and manage your tasks. Each task can have up to 20 tags.
      • If your organization has configured tag policies for DRS, add tags to tasks based on the policies. If a tag does not comply with the policies, task creation may fail. Contact your organization administrator to learn more about tag policies.
      • After a task is created, you can view its tag details on the Tags tab. For details, see Tag Management.

    If a task fails to be created, DRS retains the task for three days by default. After three days, the task automatically stops.

  3. On the Configure Source and Destination Databases page, specify source and destination database information and click Test Connection for both the source and destination databases to check whether they have been connected to the synchronization instance. After the connection tests are successful, click Next.

    Figure 5 Source database information
    Table 7 Source database settings

    Parameter

    Description

    IP Address or Domain Name

    IP address or domain name of the source DB2 for LUW database.

    Port

    The port of the source database. Range: 1 – 65535

    Database Username

    The username for accessing the source DB2 for LUW database.

    Database Password

    The password for the source database username.

    Database Name

    The name of the database to which the synchronization objects belong in the source DB2 for LUW.

    SSL Connection

    SSL encrypts the connections between the source and destination databases. If SSL is enabled, upload the SSL CA root certificate. Currently, only DB2 for LUW 10.5 and later versions support SSL. DB2 for LUW 9.7 and 10.1 do not support SSL.

    NOTE:
    • The maximum size of a single certificate file that can be uploaded is 500 KB.
    • If the SSL certificate is not used, your data may be at risk.
    • Three certificate files need to be uploaded for the DB2 for LUW SSL connection: JKS, kdb, and sth
    • DRS does not verify the kdb and sth certificates during the connection test. You need to ensure that the files are correct to prevent subsequent task failures.

    Synchronize Driver

    You need to manually add and upload the JDBC driver package corresponding to the source DB2 for LUW, and then test the connection.

    The IP address, username, and password of the source database are encrypted and stored in DRS and will be cleared after the task is deleted.

    Figure 6 Destination database information
    Table 8 Destination database settings

    Parameter

    Description

    IP Address or Domain Name

    IP address or domain name of the destination database in the IP address/Domain name:Port format. The port of the destination database. Range: 1 - 65535

    You can enter up to 10 groups of IP addresses or domain names of the destination database. Separate multiple values with commas (,). Example: 192.168.0.1:8000,192.168.0.2:8000

    Database Username

    The username for accessing the destination database.

    Database Password

    The password for the database username.

    The username and password of the destination database are encrypted and stored in DRS, and will be cleared after the task is deleted.

  4. On the Set Synchronization Task page, select the synchronization object, enter the name of the destination database, and click Next.

    Figure 7 Synchronization mode
    Table 9 Synchronization Object

    Parameter

    Description

    Synchronization Object Type

    You can select Table structure, Data, or Index for Synchronization Object Type for full synchronization.

    • Data is selected by default.
    • If Table structure is selected, the destination database cannot contain tables whose names are the same as the source tables to be synchronized.
    • If Table structure is not selected, the destination database must have tables that match the source tables, and the table structure must be the same as the selected source table structures.

    Synchronize DML

    Select the DML operations to be synchronized. By default, all DML operations are selected.

    If you do not select Delete, DELETE statements in the incremental data of the source database will not be synchronized, which may cause a data inconsistency. As a result, there may be a data conflict or the task may fail.

    Synchronization Object

    The left pane displays the source database objects, and the right pane displays the selected objects. You can select Tables or Import object files for Synchronization Object based on your service requirements.

    NOTE:
    • To quickly select the desired database objects, you can use the search function.
    • If there are changes made to the source databases or objects, click in the upper right corner to update the objects to be synchronized.
    • If an object name contains spaces, the spaces before and after the object name are not displayed. If there are two or more consecutive spaces in the middle of the object name, only one space is displayed.
    • The name of the selected synchronization object cannot contain spaces.

  5. On the Process Data page, set the filtering rules for data processing.

    • If data processing is not required, click Next.
    • If you need to filter out data, set the corresponding rules by referring to "Filtering Data" in Processing Data.

  6. On the Check Task page, check the synchronization task.

    • If any check fails, review the cause and rectify the fault. After the fault is rectified, click Check Again.

      For details about how to handle check failures, see Solutions to Failed Check Items in Data Replication Service User Guide.

    • If all check items are successful, click Next.

      You can proceed to the next step only when all checks are successful. If there are any items that require confirmation, view and confirm the details first before proceeding to the next step.

  7. On the displayed page, specify Start Time, Send Notifications, SMN Topic, Delay Threshold (s), and Stop Abnormal Tasks After, confirm that the configured information is correct, select the check box before the agreement, and click Submit to submit the task.

    Figure 8 Task startup settings

    Table 10 Task startup settings

    Parameter

    Description

    Start Time

    Set Start Time to Start upon task creation or Start at a specified time based on site requirements.

    NOTE:

    After a synchronization task is started, the performance of the source and destination databases may be affected. You are advised to start a synchronization task during off-peak hours.

    Send Notifications

    This parameter is optional. After enabled, select a SMN topic. If the status, latency metric, or data of the migration task is abnormal, DRS will send you a notification.

    SMN Topic

    This parameter is available only after you enable Send Notifications and create a topic on the SMN console and add a subscriber.

    For details, see Simple Message Notification User Guide.

    Delay Threshold (s)

    During an incremental synchronization, a synchronization delay indicates a time difference (in seconds) of synchronization between the source and destination database.

    If the synchronization delay exceeds the threshold you specify, DRS will send alarms to the specified recipients. The value ranges from 0 to 3,600. To avoid repeated alarms caused by the fluctuation of delay, an alarm is sent only after the delay has exceeded the threshold for six minutes.

    NOTE:
    • If the delay threshold is set to 0, no notifications will be sent to the recipient.
    • In the early stages of an incremental synchronization, the synchronization delay is long because a large quantity of data is awaiting synchronization. In this case, no notifications will be sent.
    • Before setting the delay threshold, enable Send Notifications.

    Data Exception Notification

    This parameter is optional. After enabled, DRS will send a notification if the task data is abnormal.

    Stop Abnormal Tasks After

    Number of days after which an abnormal task is automatically stopped. The value must range from 14 to 100. The default value is 14.

    NOTE:
    • You can set this parameter only for pay-per-use tasks.
    • Tasks in the abnormal state are still charged. If tasks remain in the abnormal state for a long time, they cannot be resumed. Abnormal tasks run longer than the period you set (unit: day) will automatically stop to avoid unnecessary fees.

  8. After the task is submitted, you can view and manage it on the Data Synchronization Management page.

    • You can view the task status. For more information about task status, see Task Statuses.
    • You can click in the upper right corner to view the latest task status.
    • By default, DRS retains a task in the Configuration state for three days. After three days, DRS automatically deletes background resources, but the task status remains unchanged. When you configure the task again, DRS applies for resources for the task again. In this case, the IP address of the DRS instance changes.
    • For a public network task, DRS needs to delete background resources after you stop the task. The EIP bound to the task cannot be restored to the Unbound state until background resources are deleted.