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dm: Cleanup typo in feature-online-ddl and update dm-faq #14481

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Sep 21, 2023
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dm: Cleanup typo in feature-online-ddl and update dm-faq #14481

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cfcbd0e
Update feature-online-ddl.md
hongshaoyang Aug 10, 2023
93def4e
Update dm-faq.md
hongshaoyang Aug 10, 2023
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Update dm-online-ddl-tool-support.md
hongshaoyang Sep 11, 2023
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8 changes: 4 additions & 4 deletions dm/dm-faq.md
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Expand Up @@ -52,7 +52,7 @@ When an exception occurs during data migration and the data migration task canno
- Specify a new task name in the task configuration file. Then execute `start-task {task-config-file}`.
- Execute `start-task --remove-meta {task-config-file}`.

## How to handle the error returned by the DDL operation related to the gh-ost table, after `online-ddl-scheme: "gh-ost"` is set?
## How to handle the error returned by the DDL operation related to the gh-ost table, after `online-ddl: true` is set?

```
[unit=Sync] ["error information"="{\"msg\":\"[code=36046:class=sync-unit:scope=internal:level=high] online ddls on ghost table `xxx`.`_xxxx_gho`\\ngithub.com/pingcap/dm/pkg/terror.(*Error).Generate ......
Expand All @@ -71,13 +71,13 @@ Therefore, in the process of incremental replication, if the specified Pos has s

You can avoid this error by the following steps:

1. Remove the `online-ddl-scheme` configuration of the task.
1. Remove the `online-ddl-scheme` or `online-ddl` configuration of the task.

2. Configure `_{table_name}_gho`, `_{table_name}_ghc`, and `_{table_name}_del` in `block-allow-list.ignore-tables`.

3. Execute the upstream DDL in the downstream TiDB manually.

4. After the Pos is replicated to the position after the gh-ost process, re-enable the `online-ddl-scheme` and comment out `block-allow-list.ignore-tables`.
4. After the Pos is replicated to the position after the gh-ost process, re-enable the `online-ddl-scheme` or `online-ddl` configuration and comment out `block-allow-list.ignore-tables`.

## How to add tables to the existing data migration tasks?

Expand Down Expand Up @@ -399,4 +399,4 @@ You can avoid this error by the following options:

## Why does the load unit report the `Unknown character set` error?

TiDB does not support all MySQL character sets. Therefore, DM reports this error if an unsupported character set is used when creating the table schema during a full import. To bypass this error, you can create the table schema in the downstream in advance using the [character sets supported by TiDB](/character-set-and-collation.md) according to the specific data.
TiDB does not support all MySQL character sets. Therefore, DM reports this error if an unsupported character set is used when creating the table schema during a full import. To bypass this error, you can create the table schema in the downstream in advance using the [character sets supported by TiDB](/character-set-and-collation.md) according to the specific data.
4 changes: 2 additions & 2 deletions dm/feature-online-ddl.md
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Expand Up @@ -8,13 +8,13 @@ aliases: ['/docs/tidb-data-migration/dev/online-ddl-scheme/','tidb-data-migratio

In production scenarios, table locking during DDL execution can block the reads from or writes to the database to a certain extent. Therefore, online DDL tools are often used to execute DDLs to minimize the impact on reads and writes. Common DDL tools are [gh-ost](https://github.com/github/gh-ost) and [pt-osc](https://www.percona.com/doc/percona-toolkit/3.0/pt-online-schema-change.html).

When using DM to migrate data from MySQL to TiDB, you can enbale online-ddl to allow collaboration of DM and gh-ost or pt-osc. For details about how to enable online-ddl and the workflow after enabling this option, see [Continuous Replication with gh-ost or pt-osc](/migrate-with-pt-ghost.md). This document focuses on the collaboration details of DM and online DDL tools.
When using DM to migrate data from MySQL to TiDB, you can enable online-ddl to allow collaboration of DM and gh-ost or pt-osc. For details about how to enable online-ddl and the workflow after enabling this option, see [Continuous Replication with gh-ost or pt-osc](/migrate-with-pt-ghost.md). This document focuses on the collaboration details of DM and online DDL tools.

## Working details for DM with online DDL tools

This section describes the working details for DM with the online DDL tools [gh-ost](https://github.com/github/gh-ost) and [pt-osc](https://www.percona.com/doc/percona-toolkit/3.0/pt-online-schema-change.html) when implementing online-schema-change.

### online-schema-change: gh-ost
## online-schema-change: gh-ost

When gh-ost implements online-schema-change, 3 types of tables are created:

Expand Down