> For the complete documentation index, see [llms.txt](https://mariadb.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mariadb.com/docs/analytics/mariadb-columnstore/architecture/mariadb-enterprise-columnstore-locking.md).

# MariaDB ColumnStore Locking

## Overview

MariaDB ColumnStore minimizes locking for analytical workloads, bulk data loads, and online schema changes.

## Lockless Reads

MariaDB ColumnStore supports lockless reads.

## Locking for Writes

MariaDB ColumnStore requires a table lock for write operations.

## Locking for Data Loading

MariaDB ColumnStore requires a write metadata lock (MDL) on the table when a bulk data load is performed with [cpimport](/docs/analytics/mariadb-columnstore/clients-and-tools/data-import/mariadb-enterprise-columnstore-data-loading-with-cpimport.md).

When a bulk data load is running:

* Read queries will not be blocked.
* Write queries and concurrent bulk data loads on the same table will be blocked until the bulk data load operation is complete, and the write metadata lock on the table has been released.
* The write metadata lock (MDL) can be monitored with the [METADATA\_LOCK\_INFO plugin](/docs/server/reference/plugins/other-plugins/metadata-lock-info-plugin.md).

For additional information, see "[MariaDB ColumnStore Data Loading](/docs/analytics/mariadb-columnstore/clients-and-tools/data-import.md)".

## Online Schema Changes

MariaDB ColumnStore supports online schema changes, so that supported DDL operations can be performed without blocking reads. The supported DDL operations only require a write metadata lock (MDL) on the target table.

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