Fix memory arbitrator links and wording

Update documentation references to use the new "memory arbitrator" naming and corrected anchor targets. Changed cross-doc links in configure-memory-usage.md and system-variables.md (e.g. tidb_mem_arbitrator_mode anchor, memory-arbitrator-mode anchor, and the high-memory alarm anchor) so they point to the renamed headings introduced for v9.0.0 and ensure consistent phrasing across the docs.

Author: hfxsd

configure-memory-usage.md

@@ -228,7 +228,7 @@ To verify the performance of `GOMEMLIMIT`, a test is performed to compare the sp
 
 ## Memory arbitrator mode
 
-Before TiDB v9.0.0, the [memory control mechanism](#how-to-configure-the-memory-usage-threshold-of-a-tidb-server-instance) has the following issues:
+Before TiDB v9.0.0, the [memory control mechanism](#configure-the-memory-usage-threshold-of-a-tidb-server-instance) has the following issues:
 
 - When the memory usage of a TiDB instance exceeds the limit, TiDB might randomly terminate running SQL statements.
 - Memory resources follow a “use-then-report” mechanism, and memory usage is isolated across different SQL statements. As a result, TiDB cannot centrally schedule or control memory resources at the instance level.
@@ -240,13 +240,13 @@ Starting from v9.0.0, TiDB introduces memory arbitrator mode. This mode introduc
 >
 > This feature is experimental and is not recommended for use in the production environment. This feature might be changed or removed without prior notice. If you find a bug, report it by submitting an [issue](https://github.com/pingcap/tidb/issues) on GitHub.
 
-You can enable memory arbitrator mode using the [`tidb_mem_arbitrator_mode`](/system-variables.md#tidb_mem_arbitrator_mode-introduced-in-v900) system variable or the `instance.tidb_mem_arbitrator_mode` parameter in the TiDB configuration file.
+You can enable memory arbitrator mode using the [`tidb_mem_arbitrator_mode`](/system-variables.md#tidb_mem_arbitrator_mode-new-in-v900) system variable or the `instance.tidb_mem_arbitrator_mode` parameter in the TiDB configuration file.
 
 - `disable`: disables memory arbitrator mode
 
 - `standard` or `priority`: enables memory arbitrator mode. After it is enabled:
     - Memory resources are used with a subscribe-before-allocation mechanism and are uniformly scheduled by the memory arbitrator in each TiDB instance.
-    - The overall memory usage of the TiDB instance is expected not to exceed the limit of [`tidb_server_memory_limit`](/system-variables.md#tidb_server_memory_limit-new-in-v640), and the [alarm for high memory usage](#alarm-for-high-memory-usage-of-tidb-server) no longer takes effect.
+    - The overall memory usage of the TiDB instance is expected not to exceed the limit of [`tidb_server_memory_limit`](/system-variables.md#tidb_server_memory_limit-new-in-v640), and the [alarm for high memory usage](#trigger-the-alarm-of-excessive-memory-usage) no longer takes effect.
     - The behavior of the following system variables remains effective:
         - [`tidb_mem_oom_action`](/system-variables.md#tidb_mem_oom_action-new-in-v610)
         - [`tidb_mem_quota_query`](/system-variables.md#tidb_mem_quota_query)

system-variables.md

@@ -4020,10 +4020,10 @@ For a system upgraded to v5.0 from an earlier version, if you have not modified
 - Type: Enum
 - Default value: `disable`
 - Possible values: `disable`, `standard`, `priority`
-- This variable sets the memory management mode of a TiDB instance. For more information, see [TiDB memory control](/configure-memory-usage.md#memory-arbitration-mode). The following values are supported:
-    - `disable` (default): Disables memory arbitration mode and keeps the mechanism of [use first and report later](/system-variables.md#tidb_server_memory_limit-new-in-v640).
-    - `standard`: Enables standard memory arbitration mode. When SQL needs to use memory resources, it first subscribes to the memory arbitrator and allocates memory resources only after the subscription succeeds. If the subscription fails, the SQL execution is terminated.
-    - `priority`: Enables priority-based memory arbitration mode. When SQL needs to use memory resources, it first subscribes to the memory arbitrator and allocates memory resources only after the subscription succeeds. TiDB handles memory resource subscription requests according to the SQL [resource group priority](/information-schema/information-schema-resource-groups.md).
+- This variable sets the memory management mode of a TiDB instance. For more information, see [TiDB memory control](/configure-memory-usage.md#memory-arbitrator-mode). The following values are supported:
+    - `disable` (default): Disables memory arbitrator mode and keeps the mechanism of [use first and report later](/system-variables.md#tidb_server_memory_limit-new-in-v640).
+    - `standard`: Enables standard memory arbitrator mode. When SQL needs to use memory resources, it first subscribes to the memory arbitrator and allocates memory resources only after the subscription succeeds. If the subscription fails, the SQL execution is terminated.
+    - `priority`: Enables priority-based memory arbitrator mode. When SQL needs to use memory resources, it first subscribes to the memory arbitrator and allocates memory resources only after the subscription succeeds. TiDB handles memory resource subscription requests according to the SQL [resource group priority](/information-schema/information-schema-resource-groups.md).
 
 ### `tidb_mem_arbitrator_query_reserved` <span class="version-mark">New in v9.0.0</span>
 
@@ -4037,7 +4037,7 @@ For a system upgraded to v5.0 from an earlier version, if you have not modified
 - Default value: `0`
 - Unit: Bytes
 - Range: `[0, 9223372036854775807]`
-- When [memory arbitration mode](/configure-memory-usage.md#memory-arbitration-mode) is enabled, this variable controls the amount of memory resources that SQL pre-subscribes to from the memory arbitrator before execution. For more information, see [TiDB memory control](/configure-memory-usage.md#manually-ensuring-memory-safety).
+- When [memory arbitrator mode](/configure-memory-usage.md#memory-arbitrator-mode) is enabled, this variable controls the amount of memory resources that SQL pre-subscribes to from the memory arbitrator before execution. For more information, see [TiDB memory control](/configure-memory-usage.md#manually-ensuring-memory-safety).
 
 ### `tidb_mem_arbitrator_soft_limit` <span class="version-mark">New in v9.0.0</span>
 
@@ -4051,7 +4051,7 @@ For a system upgraded to v5.0 from an earlier version, if you have not modified
 - Type: String
 - Default value: `0`
 - Possible values: `0`, floating-point number `(0, 1]`, integer `(1, 9223372036854775807]`
-- When [memory arbitration mode](/configure-memory-usage.md#memory-arbitration-mode) is enabled, this variable controls the upper limit of memory resources that the arbitrator can allocate in a TiDB instance. For more information, see [TiDB memory control](/configure-memory-usage.md#manually-ensuring-memory-safety).
+- When [memory arbitrator mode](/configure-memory-usage.md#memory-arbitrator-mode) is enabled, this variable controls the upper limit of memory resources that the arbitrator can allocate in a TiDB instance. For more information, see [TiDB memory control](/configure-memory-usage.md#manually-ensuring-memory-safety).
     - `0`: The default upper limit of memory resources is `95%` of the value of [`tidb_server_memory_limit`](/system-variables.md#tidb_server_memory_limit-new-in-v640)
     - Floating-point number `(0, 1]`: Specifies the upper limit of memory resources as a ratio relative to [`tidb_server_memory_limit`](/system-variables.md#tidb_server_memory_limit-new-in-v640). For example, `0.8` means the upper limit of memory resources is `tidb_server_memory_limit * 0.8`.
     - Integer `(1, 9223372036854775807]`: Specifies the number of bytes
@@ -4067,7 +4067,7 @@ For a system upgraded to v5.0 from an earlier version, if you have not modified
 - Type: Enum
 - Default value: `0`
 - Possible values: `0`, `1`, `nolimit`
-- When [memory arbitration mode](/configure-memory-usage.md#memory-arbitration-mode) is enabled, this variable controls the behavior of SQL when waiting for memory resources. For more information, see [TiDB memory control](/configure-memory-usage.md#memory-arbitration-mode).
+- When [memory arbitrator mode](/configure-memory-usage.md#memory-arbitrator-mode) is enabled, this variable controls the behavior of SQL when waiting for memory resources. For more information, see [TiDB memory control](/configure-memory-usage.md#memory-arbitrator-mode).
     - `0` (default): Disables this feature, and the variable does not take effect
     - `1`: Takes effect only in `priority` mode. SQL is automatically bound to high priority when subscribing to memory resources. When global memory resources are insufficient, the SQL execution is terminated instead of being blocked waiting.
     - `nolimit`: The memory usage of SQL is not limited by the arbitrator. This value might increase the risk of OOM on the TiDB instance.