diff --git a/system-variables.md b/system-variables.md index 3e3d830e8d255..e45f99e70d1b6 100644 --- a/system-variables.md +++ b/system-variables.md @@ -548,6 +548,13 @@ Constraint checking is always performed in place for pessimistic transactions (d - This variable is used to set the threshold value of memory quota for a query. - If the memory quota of a query during execution exceeds the threshold value, TiDB performs the operation designated by the OOMAction option in the configuration file. The initial value of this variable is configured by [`mem-quota-query`](/tidb-configuration-file.md#mem-quota-query). +### tidb_memory_usage_alarm_ratio + +- Scope: INSTANCE +- Default value: `0.8` +- TiDB triggers an alarm when the percentage of the memory it takes exceeds a certain threshold. For the detailed usage description of this feature, see [`memory-usage-alarm-ratio`](/tidb-configuration-file.md#memory-usage-alarm-ratio-new-in-v409). +- You can set the initial value of this variable by configuring [`memory-usage-alarm-ratio`](/tidb-configuration-file.md#memory-usage-alarm-ratio-new-in-v409). + ### tidb_metric_query_range_duration New in v4.0 - Scope: SESSION @@ -901,10 +908,3 @@ This variable is an alias for _transaction_isolation_. - Default value: ON - This variable controls whether to enable the dynamic memory control feature for the operator that reads data. By default, this operator enables the maximum number of threads that [`tidb_disql_scan_concurrency`](/system-variables.md#tidb_distsql_scan_concurrency) allows to read data. When the memory usage of a single SQL statement exceeds [`tidb_mem_quota_query`](/system-variables.md#tidb_mem_quota_query) each time, the operator that reads data stops one thread. - When the operator that reads data has only one thread left and the memory usage of a single SQL statement continues to exceed [`tidb_mem_quota_query`](/system-variables.md#tidb_mem_quota_query), this SQL statement triggers other memory control behaviors. - -### `tidb_memory_usage_alarm_ratio` - -- Scope: SESSION -- Default value: 0.8 -- TiDB triggers an alarm when the percentage of the memory it takes exceeds a certain threshold. For the detailed usage description of this feature, see [`memory-usage-alarm-ratio`](/tidb-configuration-file.md#memory-usage-alarm-ratio-new-in-v409). -- You can set the initial value of this variable by configuring [`memory-usage-alarm-ratio`](/tidb-configuration-file.md#memory-usage-alarm-ratio-new-in-v409).