# ALTER SYSTEM

The ALTER statement can be used to change authentication access and behaviour, global parameters, table configurations, table events, schema definitions, and indexes.

_(since v3.0.0)_

The `ALTER SYSTEM` statement is used to alter the entire datastore. It can be used to compact the system, or to set or drop a systemwide query timeout.

This statement is the only `ALTER` statement that does not have a corresponding `DEFINE` statement.

## Statement syntax

**SurrealQL Syntax**

```syntax title="SurrealQL Syntax"
ALTER SYSTEM 
    COMPACT |
    QUERY_TIMEOUT |
    DROP QUERY_TIMEOUT
```

## `QUERY_TIMEOUT` clause

A query timeout can be set for the system as a whole. The minimum possible timeout is one millisecond, below which the value will be set as `NONE`.

```surql
ALTER SYSTEM QUERY_TIMEOUT 100ns;
INFO FOR ROOT.config;
```

```surql title="Output"
{ QUERY_TIMEOUT: NONE }
```

Any value above `1ms` will set the timeout, beyond which no query that takes any longer than this will succeed.

```surql
ALTER SYSTEM QUERY_TIMEOUT 1ms;
FOR $_ IN 0..1000 {
    FOR $_ IN 0..1000 {
        CREATE |person:1000|;
    }
};

-- 'The query was not executed because it exceeded the timeout: 1ms'
```

## COMPACT clause

Compacts the entire datastore. To compact other resources, use [ALTER NAMESPACE](/docs/reference/query-language/statements/alter/namespace.md) to compact the current namespace keyspace, [ALTER DATABASE](/docs/reference/query-language/statements/alter/database.md) to compact the current database keyspace, or [ALTER TABLE](/docs/reference/query-language/statements/alter/table.md) to compact a specific table keyspace.

The actual compaction used will depend on the datastore, such as RocksDB or SurrealKV.

This clause will not work with in-memory storage which has nothing persistent to compact, producing the following error:

```surql
'The storage layer does not support compaction requests.'
```

A successful compaction will return `NONE`.

```surql
ALTER SYSTEM COMPACT;
-- NONE
```