OceanBase Migration Service

V4.2.4Enterprise Edition

OMS Documentation
OMS Introduction
- What is OMS?
- Terms
- OMS HA
- Principles of Store
- Principles of Full-Import and Incr-Sync
- Data verification principles
- Architecture
  - Overview
  - Hierarchical functional system
  - Basic components
- OMS Oracle full data migration design and impact
- Limitations
Quick Start
- Data migration process
- Data synchronization process
Deploy OMS
- Deployment types
- System and network requirements
- Memory and disk requirements
- Environment preparations
- Deploy OMS on a single node
- Deploy OMS on multiple nodes in a single region
- Deploy OMS on multiple nodes in multiple regions
- Integrate the OIDC protocol to OMS to implement SSO
- Scale out
- Check the deployment
- Deploy a time-series database (Optional)
OMS console
- Log in to the OMS console
- Overview
- User center
  - Configure user information
  - Change your login password
  - Log out
Data migration
- Overview
- Migrate data from a MySQL database to a MySQL-compatible tenant of OceanBase Database
- Migrate data from a MySQL-compatible tenant of OceanBase Database to a MySQL database
- Migrate data from an Oracle database to a MySQL-compatible tenant of OceanBase Database
- Migrate data from an Oracle-compatible tenant of OceanBase Database to an Oracle database
- Migrate data from an Oracle database to an Oracle-compatible tenant of OceanBase Database
- Migrate data from a DB2 LUW database to an Oracle-compatible OceanBase database
- Migrate data from an Oracle-compatible tenant of OceanBase Database to a DB2 LUW database
- Migrate data from a DB2 LUW database to a MySQL-compatible tenant of OceanBase Database
- Migrate data from a MySQL-compatible tenant of OceanBase Database to a DB2 LUW database
- Migrate data within OceanBase Database
- Create an active-active disaster recovery task in OceanBase Database
- Migrate data from a TiDB database to a MySQL-compatible tenant of OceanBase Database
- Migrate data from a PostgreSQL database to a MySQL-compatible tenant of OceanBase Database
- Migrate data from a PolarDB-X 1.0 database to a MySQL-compatible tenant of OceanBase Database
- Migrate incremental data from an Oracle-compatible tenant of OceanBase Database to a MySQL database
- Manage data migration tasks
  - View details of a data migration task
  - Rename a data migration task
  - View and modify migration objects
  - Use tags to Manage data migration tasks
  - Perform batch operations on data migration tasks
  - Download and import settings of migration objects
  - View and modify the parameter configurations of a data migration task
  - Start and pause a data migration task
  - Release and delete a data migration task
- Supported DDL operations and limits for synchronization
  - Synchronize DDL operations from a MySQL database to a MySQL-compatible tenant of OceanBase Database
    - Overview
    - CREATE TABLE
      - Create a table
      - Create a column
      - Create an index or a constraint
      - Create partitions
    - Data type conversion
    - ALTER TABLE
      - Modify a table
      - Operations on columns
      - Operations on constraints and indexes
      - Operations on partitions
    - TRUNCATE TABLE
    - RENAME TABLE
    - DROP TABLE
    - CREATE INDEX
    - DROP INDEX
    - DDL incompatibilities between a MySQL database and a MySQL-compatible tenant of OceanBase Database
      - Overview
      - Incompatibilities of the CREATE TABLE statement
        Incompatibilities of CREATE TABLE
        Column types that are supported to create indexes or constraints
      - Incompatibilities of the ALTER TABLE statement
        Incompatibilities of ALTER TABLE
        Change the type of a constrained column
        Change the type of an unconstrained column
        Change the length of a constrained column
        Change the length of an unconstrained column
        Delete a constrained column
      - Incompatibilities of DROP INDEX operations
  - Synchronize DDL operations from a MySQL-compatible tenant of OceanBase Database to a MySQL database
  - DDL operations for synchronizing data from an Oracle database to an Oracle-compatible tenant of OceanBase Database
    - Overview of DDL synchronization from Oracle to an Oracle-compatible tenant of OceanBase Database
    - CREATE TABLE
      - Overview
      - Create a relational table
        Create a relational table
        Define columns of a relational table
      - Virtual columns
      - Regular columns
      - Create partitions
        Overview
        Partitioning
        Subpartitioning
        Composite partitioning
        User-defined partitioning
        Subpartition templates
      - Constraints
        Overview
        Inline constraints
        Out-of-line constraints
    - CREATE INDEX
      - Overview
      - Normal indexes
    - ALTER TABLE
      - Modify tables
      - Modify, drop, and add table attributes
      - Column attribute management
        Modify, drop, and add column attributes
        Rename a column
        Add columns and column attributes
        Modify column attributes
        Drop columns
      - Modify, drop, and add constraints
      - Partition management
        Modify, drop, and add partitions
        Drop partitions
        Drop subpartitions
        Add partitions and subpartitions
        Modify partitions
        Truncate partitions
    - DROP TABLE
    - RENAME OBJECT
    - TRUNCATE TABLE
    - DROP INDEX
    - DDL incompatibilities between an Oracle database and an Oracle-compatible tenant of OceanBase Database
      - Overview
      - Incompatibilities of CREATE TABLE
      - Incompatibilities in table modification operations
        Incompatibilities of ALTER TABLE
        Change the type of a constrained column
        Change the type of an unconstrained column
        Change the length of a constrained column
        Change the length of an unconstrained column
  - DDL synchronization from an Oracle-compatible tenant of OceanBase Database to an Oracle database
  - Synchronize DDL operations from a DB2 LUW database to an Oracle-compatible tenant of OceanBase Database
  - Synchronize DDL operations from an Oracle-compatible tenant of OceanBase Database to a DB2 LUW database
  - Synchronize DDL operations from a DB2 LUW database to a MySQL-compatible tenant of OceanBase Database
  - Synchronize DDL operations from a MySQL-compatible tenant of OceanBase Database to a DB2 LUW database
  - DDL synchronization between MySQL-compatible tenants of OceanBase Database
  - DDL synchronization between Oracle-compatible tenants of OceanBase Database
Data synchronization
- Overview
- Synchronize data from OceanBase Database to a Kafka instance
- Synchronize data from OceanBase Database to a RocketMQ instance
- Synchronize data from OceanBase Database to a DataHub instance
- Synchronize data from an ODP logical table to a physical table in a MySQL-compatible tenant of OceanBase Database
- Synchronize data from an ODP logical table to a DataHub instance
- Synchronize data from an IDB logical table to a physical table in a MySQL-compatible tenant of OceanBase Database
- Synchronize data from an IDB logical table to a DataHub instance
- Synchronize data from a MySQL database to a DataHub instance
- Synchronize data from an Oracle database to a DataHub instance
- Manage data synchronization tasks
  - View details of a data synchronization task
  - Change the name of a data synchronization task
  - View and modify synchronization objects
  - Use tags to Manage data synchronization tasks
  - Perform batch operations on data synchronization tasks
  - Download and import the settings of synchronization objects
  - View and modify the parameter configurations of a data synchronization task
  - Start and pause a data synchronization task
  - Release and delete a data synchronization task
Create and manage data sources
- Create data sources
  - Create an OceanBase data source
    - Create a physical OceanBase data source
    - Create an ODP data source
    - Create an IDB data source
    - Create a public cloud OceanBase data source
  - Create a MySQL data source
  - Create an Oracle data source
  - Create a TiDB data source
  - Create a Kafka data source
  - Create a RocketMQ data source
  - Create a DataHub data source
  - Create a DB2 LUW data source
  - Create a PostgreSQL data source
  - Create a PolarDB-X 1.0 data source
- Manage data sources
  - View data source information
  - Copy a data source
  - Edit a data source
  - Delete a data source
- Create a database user
- User privileges
- Enable binlogs for the MySQL database
- Minimum privileges required when an Oracle database serves as the source
OPS & Monitoring
- O&M overview
- Go to the overview page
- Server
  - View server information
  - Update the quota
  - View server logs
- Components
  - Store
    - Create a store
    - View details of a store
    - Update the configurations of a store
    - Start and pause a store
    - Delete a store
  - Incr-Sync
    - View details of an Incr-Sync component
    - Start and pause an Incr-Sync component
    - Migrate an Incr-Sync component
    - Update the configurations of an Incr-Sync component
    - Batch O&M
    - Delete an Incr-Sync component
  - Full-Import
    - View details of a Full-Import component
    - Pause a Full-Import component
    - Rerun and resume a Full-Import component
    - Update the configurations of a Full-Import component
    - Delete a Full-Import component
  - Full-Verification
    - View details of a Full-Verification component
    - Pause a Full-Verification component
    - Rerun and resume a Full-Verification component
    - Update the configurations of a Full-Verification component
    - Delete a Full-Verification component
- O&M Task
  - View O&M tasks
  - Skip a task or subtask
  - Retry a task or subtask
- Parameter Template
  - Overview
  - Task Template
    - Create a task template
    - View and edit task templates
    - Copy and export a task template
    - Delete a task template
  - Component Template
    - Create a component template
    - View and edit component templates
    - Copy and export a component template
    - Delete a component template
  - Component parameters
    - Store parameters
    - Incr-Sync parameters
    - Full-Import parameters
    - Full-Verification parameters
    - CM parameters
    - Supervisor parameters
System management
- Permission Management
  - Overview
  - Manage users
  - Manage departments
- Alert center
  - View task alerts
  - View system alerts
  - Manage alert settings
- Associate with OCP
- System parameters
  - Modify system parameters
  - Modify HA configurations
  - oblogproxy parameters
- Operation audit
Troubleshooting Guide
- Manage OMS services
- OMS logs
- Component O&M
  - O&M operations for the Supervisor component
  - CLI-based O&M for the Connector component
  - O&M operations for the Store component
- Component tuning
  - Incr-Sync/Full-Import tuning
  - Oracle store tuning
- Set throttling
- Store performance diagnostics
Reference Guide
- Features
  - Configure DDL/DML synchronization
  - Supported DDL operations for synchronization
  - Rename a migration or synchronization object
  - Use SQL conditions to filter data
  - Set an incremental synchronization timestamp
  - Configure matching rules
  - Wildcard patterns supported for matching rules
  - Hidden column mechanisms
  - Instructions on schema migration
  - Create and update a heartbeat table
  - Change the topic
  - Column filtering
  - Data formats
- API Reference
  - Overview
  - CreateProject
  - StartProject
  - StopProject
  - ResumeProject
  - ReleaseProject
  - DeleteProject
  - ListProjects
  - DescribeProject
  - DescribeProjectSteps
  - DescribeProjectStepMetric
  - DescribeProjectProgress
  - DescribeProjectComponents
  - ListProjectFullVerifyResult
  - StartProjectsByLabel
  - StopProjectsByLabel
  - CreateMysqlDataSource
  - CreateOceanBaseDataSource
  - CreateOceanBaseODPDataSource
  - CreatePolarDBDataSource
  - ListDataSource
  - CreateLabel
  - ListAllLabels
  - DeleteDataSource
  - CreateProjectModifyRecords
  - ListProjectModifyRecords
  - StopProjectModifyRecords
  - RetryProjectModifyRecords
  - CancelProjectModifyRecord
  - SubmitPreCheck
  - GetPreCheckResult
  - UpdateProjectConfig
- Alert Reference
  - oms_host_down
  - oms_host_down_migrate_resource
  - oms_host_threshold
  - oms_migration_failed
  - oms_migration_delay
  - oms_sync_failed
  - oms_sync_status_inconsistent
  - oms_sync_delay
- OMS error codes
- SQL statements for querying table objects
- Create a trigger
- Change the log level for a PostgreSQL instance
- Online DDL tools
- Oracle supplemental logging
Upgrade Guide
- Overview
- Upgrade OMS in single-node deployment mode
- Upgrade OMS in multi-node deployment mode
- FAQ
FAQ
- General O&M
  - How do I modify the resource quotas of an OMS container?
  - How do I troubleshoot the OMS server down issue?
  - Deploy InfluxDB for OMS
  - Increase the disk space of the OMS host
- Task diagnostics
  - How do I troubleshoot common problems with Oracle Store?
  - How do I perform performance tuning for Oracle Store?
  - What do I do when Oracle Store reports an error at the isUpdatePK stack?
  - What do I do when a store does not have data of the timestamp requested by the downstream?
  - What do I do when OceanBase Store failed to access an OceanBase cluster through RPC?
  - How do I use LogMiner to pull data from an Oracle database?
- OPS & monitoring
  - What are the alert rules?
- Data synchronization
  - FAQ about synchronization to a message queue
    - What are the strategies for ensuring the message order in incremental data synchronization to Kafka
- Data migration
  - User privileges
    - What privileges do I need to grant to a user during data migration to or from an Oracle database?
  - Full migration
    - How do I query the ID of a checker?
    - How do I query log files of the Checker component of OMS?
    - How do I query the verification result files of the Checker component of OMS?
    - What do I do if the destination table does not exist?
    - What can I do when the full migration failed due to LOB fields?
    - What do I do if garbled characters cannot be written into OceanBase Database V3.1.2?
  - Incremental synchronization
    - How do I skip DDL statements?
    - How do I migrate an Oracle database object whose name exceeds 30 bytes in length?
    - How do I update whitelists and blacklists?
    - What are the application scope and limits of ETL?
- Installation and deployment
  - How do I upgrade Store?
Release Note
- V4.2
  - OMS V4.2.4
  - OMS V4.2.3
  - OMS V4.2.2
  - OMS V4.2.1
  - OMS V4.2.0
- V4.1
  - OMS V4.1.0
- V4.0
  - OMS V4.0.2
  - OMS V4.0.1
- V3.4
  - OMS V3.4.0
- V3.3
  - OMS V3.3.1
  - OMS V3.3.0
- V3.2
  - OMS V3.2.2
  - OMS V3.2.1
- V3.1
  - OMS V3.1.0
- V2.1
  - OMS V2.1.2
  - OMS V2.1.0

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Change the length of an unconstrained column

Last Updated：2025-05-12 01:56:25 Updated

This topic describes incompatibilities between MySQL databases and MySQL-compatible tenants of OceanBase Database when you change the length of an unconstrained column.

The following table describes the operations that you can perform to change the length of a column by executing the ALTER TABLE table_name MODIFY/CHANGE COLUMN DDL statement in a MySQL database and a MySQL-compatible tenant of OceanBase Database.

Note

In the table, a hyphen (-) indicates none.

Column type in a MySQL database	Allowed operation	Column type in a MySQL-compatible tenant of OceanBase Database	Allowed operation
INT	Increase and decrease the length	INTEGER	Increase and decrease the length
TINYINT	Increase and decrease the length	TINYINT	Increase and decrease the length
SMALLINT	Increase and decrease the length	SMALLINT	Increase and decrease the length
MEDIUMINT	Increase and decrease the length	MEDIUMINT	Increase and decrease the length
BIGINT	Increase and decrease the length	BIGINT	Increase and decrease the length
BOOL	-	BOOLEAN	-
DECIMAL	Increase and decrease the length	DECIMAL	Increase the length
NUMERIC	Increase and decrease the length	NUMERIC	Increase the length
REAL	Increase and decrease the length	FLOAT	Increase and decrease the length
DOUBLE	Increase and decrease the length	DOUBLE	Increase and decrease the length
FLOAT	Increase and decrease the length	FLOAT	Increase and decrease the length
BIT	Increase and decrease the length	BIT	Increase and decrease the length
CHAR	Increase and decrease the length	CHAR	Increase the length
NCHAR	Increase and decrease the length	CHAR	Increase the length
VARCHAR	Increase and decrease the length	VARCHAR	Increase the length
BINARY	Increase and decrease the length	BINARY	-
VARBINARY	Increase and decrease the length	VARBINARY	Increase the length
LONG_VARBINARY	-	BLOB	-
YEAR	Increase and decrease the length	YEAR	Increase the length (the length is fixed to be 4 bytes)
DATE	-	DATE	-
TIME	Increase and decrease the length	TIME	Increase the length
TIMESTAMP	Increase and decrease the length	TIMESTAMP	Increase the length
DATETIME	Increase and decrease the length	DATETIME	Increase the length
TINYBLOB	-	TINYBLOB	-
MEDIUMBLOB	-	MEDIUMBLOB	-
BLOB	-	BLOB	-
LONGBLOB	-	LONGBLOB	-
TINYTEXT	-	TINYTEXT	-
MEDIUMTEXT	-	MEDIUMTEXT	-
TEXT	-	TEXT	-
LONGTEXT	-	LONGTEXT	-
ENUM	Increase and decrease the length	ENUM	Increase the length
SET	Increase and decrease the length	SET	Increase the length
JSON	-	JSON	-

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