# Use of DM - Configure Whether to Do Database Sharding Merges

__*Using DM*__
__*sharded table shard merge*__

```
name: test                    
shard-mode: "pessimistic"   
```
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If it is a data migration scenario where shard tables are merged, and the DDL of the database sharding needs to be synchronized, you must explicitly configure shard-mode, otherwise do not configure this option.
There are many problems with shard shard DDL synchronization. Please make sure you understand the principles and limitations of DM synchronization shard shard DDL, and use it with caution.

## Task Information Configuration*********
name: test # The task name, must be globally unique
shard-mode: "pessimistic" # The default value is "", meaning no coordination is required. Set the pessimistic coordination mode to "pessimistic" if it is a database sharding merge task. Optimistic coordination mode can also be set to "optimistic" after learning more about the principles and usage limitations of optimistic coordination mode