# VACUUM
<a name="vacuum-statement"></a>

The `VACUUM` statement performs table maintenance on Apache Iceberg tables by performing [snapshot expiration](https://iceberg.apache.org/docs/latest/spark-procedures/#expire_snapshots) and [orphan file removal](https://iceberg.apache.org/docs/latest/spark-procedures/#remove_orphan_files).

**Note**  
`VACUUM` is transactional and is supported only for Apache Iceberg tables in Athena engine version 3.

The `VACUUM` statement optimizes Iceberg tables by reducing storage consumption. For more information about using `VACUUM`, see [Optimize Iceberg tables](querying-iceberg-data-optimization.md). Note that, because the `VACUUM` statement makes API calls to Amazon S3, charges apply for the associated requests to Amazon S3.

**Warning**  
If you run a snapshot expiration operation, you can no longer time travel to expired snapshots.

## Synopsis
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To remove data files no longer needed for an Iceberg table, use the following syntax.

```
VACUUM [{{database_name}}.]{{target_table}}
```
+ `VACUUM` expects the Iceberg data to be in an Amazon S3 folder rather than an Amazon S3 bucket. For example, if your Iceberg data is at `s3://amzn-s3-demo-bucket`/ instead of `s3://amzn-s3-demo-bucket/myicebergfolder/`, the `VACUUM` statement fails with the error message GENERIC\_INTERNAL\_ERROR: Path missing in file system location: `s3://amzn-s3-demo-bucket`.
+ For `VACUUM` to be able to delete data files, your query execution role must have `s3:DeleteObject` permissions on the bucket where your Iceberg tables, metadata, snapshots, and data files are located. If the permission is not present, the `VACUUM` query will succeed, but the files will not be deleted. 
+ To run `VACUUM` on a table with a name that begins with an underscore (for example, `_mytable`), enclose the table name in backticks, as in the following example. If you prefix the table name with a database name, do not enclose the database name in backticks. Note that double quotes will not work in place of backticks. 

  This behavior is particular to `VACUUM`. The `CREATE` and `INSERT INTO` statements do not require backticks for table names that begin with underscores.

  ```
  VACUUM `_mytable`
  VACUUM my_database.`_mytable`
  ```

## Operations performed
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`VACUUM` performs the following operations:
+ Removes snapshots that are older than the amount of time that is specified by the `vacuum_max_snapshot_age_seconds` table property. By default, this property is set to 432000 seconds (5 days).
+ Removes snapshots that are not within the period to be retained that are in excess of the number specified by the `vacuum_min_snapshots_to_keep` table property. The default is 1.

  You can specify these table properties in your `CREATE TABLE` statement. After the table has been created, you can use the [ALTER TABLE SET TBLPROPERTIES](querying-iceberg-alter-table-set-properties.md) statement to update them. 
+ Removes any metadata and data files that are unreachable as a result of the snapshot removal. You can configure the number of old metadata files to be retained by setting the `vacuum_max_metadata_files_to_keep` table property. The default value is 100.
+ Removes orphan files that are older than the time specified in the `vacuum_max_snapshot_age_seconds` table property. Orphan files are files in the table's data directory that are not part of the table state.

For more information about creating and managing Apache Iceberg tables in Athena, see [Create Iceberg tables](querying-iceberg-creating-tables.md) and [Manage Iceberg tables](querying-iceberg-managing-tables.md).