THROTTLE

Description

This statement is used to throttle SQL requests based on specific features. It allows requests that meet the throttling criteria to fail early, preventing them from affecting normal requests.

Syntax

alter_system_throttle_stmt:
    ALTER SYSTEM throttle_action;

throttle_action:
      ENABLE SQL THROTTLE [priority_option] [using_metric_option_list]
    | DISABLE SQL

priority_option:
    FOR PRIORITY <= INT_VALUE

using_metric_option_list:
    USING metric_option_list

metric_option_list:
    metric_option [metric_option ...]

metric_option:
      RT = {INT_VALUE | DECIMAL_VALUE}
    | CPU = {INT_VALUE | DECIMAL_VALUE}
    | IO = INT_VALUE
    | NETWORK = {INT_VALUE | DECIMAL_VALUE}
    | QUEUE_TIME = {INT_VALUE | DECIMAL_VALUE}
    | LOGICAL_READS = {INT_VALUE | DECIMAL_VALUE}

Parameters

Parameter	Description
ENABLE SQL	Enables throttling, followed by the throttling feature and its value.
FOR PRIORITY	Specifies the priority level affected by throttling, ensuring that throttling only affects certain sessions. You can set the priority for the current session using the session-level variable sql_throttle_priority, which defaults to -1. For example, if sessions a, b, and c have priorities 1, 2, and 3 respectively, setting ALTER SYSTEM ENABLE SQL THROTTLE FOR PRIORITY <= 2 USING QUEUE_TIME=0.1; means that sessions a and b are affected by throttling, while session c is not.
RT	Throttles based on SQL response time (Response Time). Unit: seconds.
CPU	Throttles based on CPU usage. This parameter is not supported in the current version.
IO	Throttles based on I/O operations. This parameter is not supported in the current version.
NETWORK	Throttles based on the amount of network traffic transmitted. This parameter is not supported in the current version.
QUEUE_TIME	Throttles based on queue wait time. Unit: seconds.
LOGICAL_READS	Throttles based on the number of logical reads. This parameter is not supported in the current version.
DISABLE SQL	Disables throttling.

Examples

Throttle requests with a queue wait time exceeding 0.1s for sessions with a priority less than or equal to 100.

ALTER SYSTEM ENABLE SQL THROTTLE FOR PRIORITY <= 100 USING QUEUE_TIME=0.1;