# Cluster Level Locks

* Only one cluster level lock can be taken at a time.
* If a cluster level lock is taken, it will block any database locks from being taken.
* DML operations are not affected by these locks.
* DDL operations that are affected by these locks are listed in [Operations that Take Cluster Level Locks](https://docs.singlestore.com/db/v9.1/reference/sql-reference/operations-that-take-either-a-database-or-a-cluster-level-lock/operations-that-take-cluster-level-locks.md)
* Any blocked operations will queue.

Example: `ADD LEAF` is running on the cluster. While the operation is running, `CREATE TABLE` tries to run, but is blocked until `ADD LEAF` completes.

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Modified at: August 30, 2022

Source: [/db/v9.1/reference/sql-reference/operations-that-take-either-a-database-or-a-cluster-level-lock/cluster-level-locks/](https://docs.singlestore.com/db/v9.1/reference/sql-reference/operations-that-take-either-a-database-or-a-cluster-level-lock/cluster-level-locks/)

(An index of the documentation is available at /llms.txt)