Database Migration Module

Item

Prerequisites

Migration of Multi-version Databases

The database of this version can be migrated to a database of the same or a higher version, but not a database of an earlier version.

Task Limit

See Before You Begin and Requirements described in the Task Configuration section based on your action type. For example, if you want to migrate from self-built MySQL to self-built MySQL, see restrictions in User Guide > Database Migration Service Module > Data Transfer > Data Migration > Task Creation > Configure a Migration Task with Self-built MySQL as Source > Migrate from Self-built MySQL to Self-built MySQL.

Migration Speed

The migration speed depends on the number and size of tables on the source server, bandwidth, and transmission distance over the Internet.

Pullup and Support Limit of Complex Applications

When transmitting complex businesses, record business information, and migrate, switch, and test business systems as needed. During application switching, you must stop related service processes to ensure consistency. After switching, relevant personnel familiar with the businesses should test and verify the migration so as to reduce downtime.

Specific Requirements

If there are specific requirements such as confidential files and IP addresses that need to remain unchanged, you must submit a ticket for technical consultation to meet the corresponding requirements.

Single Task and Upper Limit of Migration Tasks

A single task can process a maximum of 500 tables at a time, and each user can execute 50 tasks concurrently.

Configuration Limit of Migration Node

The server where the migration node is located must have a memory larger than 8 GB, a CPU larger than four cores, and a Linux kernel larger than 3.10.

Character Limit

Database, table, and column names must not contain dashes (-), for example, test-db.

Ensure that the character sets of the source and target databases are compatible or consistent. Otherwise, data inconsistency or failure may occur.

Limit of Migration/Subscription/Subscription Task

Before configuring tasks, carefully read the parameter requirements and database requirements in task creation topics in the User Guide, Database Migration Service Module, and Data Transfer sections.

You currently cannot incrementally migrate, synchronize, subscribe to, and audit and repair tables without primary keys and tables with multiple primary keys.

Synchronization/subscription is applicable only to scenarios with less than 1000 records/second. Do not use these two features in scenarios such as synchronization between medium- and large-scale intensive services and disaster recovery.

For migration, synchronization, and subscription tasks, all types of changes including UPDATE, INSERT, and DELETE actions can be transmitted after tasks are started, while structural changes cannot be transmitted during the migration process.

Do not change DDL operations that change the library, table, or column structure when the task is running. Otherwise, the migration task will fail.

System libraries, system modes, system tables, and temporary tables cannot be migrated.

Ensure that no active/standby database switchover occurs during the migration. Otherwise, the migration fails.

Ensure that database information (IP address, port number, user name, and password) does not change during migration. Otherwise, the migration fails.

If you perform only full data migration, do not write new data to the source database. Otherwise, the source and target data may be inconsistent.

Only one database can be migrated in a single data migration task. To migrate multiple databases, configure a data migration task for each database.

The cooperation between users and businesses is required to maintain data consistency. Do not update the same primary key data on two service nodes. Otherwise, primary keys may conflict or overwrite each other.

Configuration Limit of Migration Source and Target

The disk space of the target database should be at least 1.2 times that of the source database, because the data migration may cause table fragmentation in the target database due to concurrent INSERT operations.

The CPU and disk usage of the server where the source and target libraries reside must be less than 90% because the transmission consumes certain resources.