ALTER SYSTEM

ALTER SYSTEM is available in SDK v5+.

The ALTER SYSTEM statement provides runtime configuration management, allowing you to change system parameters dynamically.

Syntax

DQL

ALTER SYSTEM SET parameter_name TO value
ALTER SYSTEM SET parameter_name = value
ALTER SYSTEM RESET parameter_name
ALTER SYSTEM RESET ALL

SET Parameter

Change a configuration parameter to a specific value:

DQL

-- Using TO syntax
ALTER SYSTEM SET DQL_STRICT_MODE TO false

-- Using = syntax (equivalent)
ALTER SYSTEM SET DQL_STRICT_MODE = false

Set to DEFAULT

Reset a parameter to its default value using the DEFAULT keyword:

DQL

ALTER SYSTEM SET parameter_name TO DEFAULT

RESET Parameter

Reset a configuration parameter to its default value:

DQL

-- Reset single parameter
ALTER SYSTEM RESET DQL_STRICT_MODE

-- Reset all parameters to defaults
ALTER SYSTEM RESET ALL

Parameter Values

Parameter values can be:

Literals: Numbers, strings, booleans
- Boolean: true, false
- Integer: 100, 5000
- String: 'value' or "value"
DEFAULT keyword: Resets to the default value

Available DQL Configuration Parameters

DQL_STRICT_MODE

Type: Boolean Default: true Controls whether strict mode is enabled for collection type definitions.

DQL

ALTER SYSTEM SET DQL_STRICT_MODE TO false

See Strict Mode for more information.

DQL_DEFAULT_DIRECTIVES

Type: Object (JSON) Default: {} Sets default query directives that apply to all queries. Individual query directives can override these defaults.

DQL

-- Set default directives for development
ALTER SYSTEM SET DQL_DEFAULT_DIRECTIVES = {"#reprepare": true, "#max_serial_ranges": 2}

-- Reset to no default directives
ALTER SYSTEM SET DQL_DEFAULT_DIRECTIVES = {}

See Directives for more information.

DQL_CONCURRENT_REQUEST_LIMIT

Type: Integer Default: System-dependent Limits the number of concurrent DQL requests that can execute simultaneously. When the limit is reached, additional requests are queued until capacity becomes available.

DQL

-- Limit to 10 concurrent requests
ALTER SYSTEM SET DQL_CONCURRENT_REQUEST_LIMIT TO 10

-- Reset to default (no limit)
ALTER SYSTEM RESET DQL_CONCURRENT_REQUEST_LIMIT

This parameter helps prevent resource exhaustion under heavy query load by controlling the maximum number of queries running at once.

Available Transport Configuration Parameters

tcp_server_bind_mdns_server_port

Type: Integer Default: Random port Specifies the port that a Small Peer SDK instance uses for mDNS announcements and incoming LAN (TCP) connections on the local device. Setting an explicit port is useful when you need to traverse a VLAN or firewall by scanning for open ports, or when you need a deterministic port for network policy. Leaving the parameter unset preserves the default behavior of binding to a random port.

DQL

ALTER SYSTEM SET tcp_server_bind_mdns_server_port TO 1234

If you run multiple Ditto applications on the same device — for example a debug or TestFlight build alongside a production build — each application must use a unique port. Otherwise only one application will be able to establish LAN connections at a time.

tcp_server_bind_mdns_server_port must be set before sync is started for the value to take effect.

let result = try await ditto.store.execute(
  query: "ALTER SYSTEM SET tcp_server_bind_mdns_server_port TO 1234"
)

val result = ditto.store.execute("ALTER SYSTEM SET tcp_server_bind_mdns_server_port TO 1234")

const result = await ditto.store.execute("ALTER SYSTEM SET tcp_server_bind_mdns_server_port TO 1234");

DittoQueryResult result = ditto.store.execute("ALTER SYSTEM SET tcp_server_bind_mdns_server_port TO 1234");

var result = await ditto.Store.ExecuteAsync("ALTER SYSTEM SET tcp_server_bind_mdns_server_port TO 1234");

auto result = ditto.get_store().execute("ALTER SYSTEM SET tcp_server_bind_mdns_server_port TO 1234").get();

let result = ditto.store()
    .execute_v2((
        "ALTER SYSTEM SET tcp_server_bind_mdns_server_port TO 1234",
        serde_json::json!({})
    ))
    .await?;

final result = await ditto.store.execute("ALTER SYSTEM SET tcp_server_bind_mdns_server_port TO 1234");

See Local Area Network for the underlying mDNS, TCP, and firewall behavior this parameter affects.

Common Use Cases

Enable/Disable Strict Mode

DQL

-- Disable strict mode to allow flexible type definitions
ALTER SYSTEM SET DQL_STRICT_MODE TO false

-- Re-enable strict mode
ALTER SYSTEM SET DQL_STRICT_MODE TO true

Configure Default Query Directives

DQL

-- Set default directives during development
ALTER SYSTEM SET DQL_DEFAULT_DIRECTIVES = {"#reprepare": true}

-- Clear default directives for production
ALTER SYSTEM SET DQL_DEFAULT_DIRECTIVES = {}

Control Concurrent Query Execution

DQL

-- Limit concurrent queries to prevent overload
ALTER SYSTEM SET DQL_CONCURRENT_REQUEST_LIMIT TO 20

-- Remove limit
ALTER SYSTEM RESET DQL_CONCURRENT_REQUEST_LIMIT

Reset All Configuration

DQL

-- Reset all parameters to their default values
ALTER SYSTEM RESET ALL

Examples

// Set strict mode
await ditto.store.execute(
  query: "ALTER SYSTEM SET DQL_STRICT_MODE TO false"
)

// Reset parameter
await ditto.store.execute(
  query: "ALTER SYSTEM RESET DQL_STRICT_MODE"
)

// Reset all parameters
await ditto.store.execute(
  query: "ALTER SYSTEM RESET ALL"
)

// Set strict mode
ditto.store.execute("ALTER SYSTEM SET DQL_STRICT_MODE TO false")

// Reset parameter
ditto.store.execute("ALTER SYSTEM RESET DQL_STRICT_MODE")

// Reset all parameters
ditto.store.execute("ALTER SYSTEM RESET ALL")

// Set strict mode
await ditto.store.execute("ALTER SYSTEM SET DQL_STRICT_MODE TO false");

// Reset parameter
await ditto.store.execute("ALTER SYSTEM RESET DQL_STRICT_MODE");

// Reset all parameters
await ditto.store.execute("ALTER SYSTEM RESET ALL");

// Set strict mode
ditto.store.execute("ALTER SYSTEM SET DQL_STRICT_MODE TO false");

// Reset parameter
ditto.store.execute("ALTER SYSTEM RESET DQL_STRICT_MODE");

// Reset all parameters
ditto.store.execute("ALTER SYSTEM RESET ALL");

// Set strict mode
await ditto.Store.ExecuteAsync("ALTER SYSTEM SET DQL_STRICT_MODE TO false");

// Reset parameter
await ditto.Store.ExecuteAsync("ALTER SYSTEM RESET DQL_STRICT_MODE");

// Reset all parameters
await ditto.Store.ExecuteAsync("ALTER SYSTEM RESET ALL");

// Set strict mode
ditto.get_store().execute("ALTER SYSTEM SET DQL_STRICT_MODE TO false").get();

// Reset parameter
ditto.get_store().execute("ALTER SYSTEM RESET DQL_STRICT_MODE").get();

// Reset all parameters
ditto.get_store().execute("ALTER SYSTEM RESET ALL").get();

// Set strict mode
ditto.store()
    .execute_v2((
        "ALTER SYSTEM SET DQL_STRICT_MODE TO false",
        serde_json::json!({})
    ))
    .await?;

// Reset parameter
ditto.store()
    .execute_v2((
        "ALTER SYSTEM RESET DQL_STRICT_MODE",
        serde_json::json!({})
    ))
    .await?;

// Reset all parameters
ditto.store()
    .execute_v2((
        "ALTER SYSTEM RESET ALL",
        serde_json::json!({})
    ))
    .await?;

// Set strict mode
await ditto.store.execute("ALTER SYSTEM SET DQL_STRICT_MODE TO false");

// Reset parameter
await ditto.store.execute("ALTER SYSTEM RESET DQL_STRICT_MODE");

// Reset all parameters
await ditto.store.execute("ALTER SYSTEM RESET ALL");

Checking Current Values

To verify the current value of a parameter after changing it, use the SHOW statement:

DQL

-- Set parameter
ALTER SYSTEM SET DQL_STRICT_MODE TO false

-- Verify the change
SHOW DQL_STRICT_MODE

Configuration changes made with ALTER SYSTEM are runtime only and do not persist across restarts. To apply settings on every startup, set the parameters in your Ditto instance configuration before starting.

Statements

Types and Functions

Reference

ALTER SYSTEM

Syntax

SET Parameter

Set to DEFAULT

RESET Parameter

Parameter Values

Available DQL Configuration Parameters

DQL_STRICT_MODE

DQL_DEFAULT_DIRECTIVES

DQL_CONCURRENT_REQUEST_LIMIT

Available Transport Configuration Parameters

tcp_server_bind_mdns_server_port

Common Use Cases

Enable/Disable Strict Mode

Configure Default Query Directives

Control Concurrent Query Execution

Reset All Configuration

Examples

Checking Current Values

See Also

​Syntax

​SET Parameter

​Set to DEFAULT

​RESET Parameter

​Parameter Values

​Available DQL Configuration Parameters

​DQL_STRICT_MODE

​DQL_DEFAULT_DIRECTIVES

​DQL_CONCURRENT_REQUEST_LIMIT

​Available Transport Configuration Parameters

​tcp_server_bind_mdns_server_port

​Common Use Cases

​Enable/Disable Strict Mode

​Configure Default Query Directives

​Control Concurrent Query Execution

​Reset All Configuration

​Examples

​Checking Current Values

​See Also

Syntax

SET Parameter

Set to DEFAULT

RESET Parameter

Parameter Values

Available DQL Configuration Parameters

DQL_STRICT_MODE

DQL_DEFAULT_DIRECTIVES

DQL_CONCURRENT_REQUEST_LIMIT

Available Transport Configuration Parameters

tcp_server_bind_mdns_server_port

Common Use Cases

Enable/Disable Strict Mode

Configure Default Query Directives

Control Concurrent Query Execution

Reset All Configuration

Examples

Checking Current Values

See Also