DM 监听线程：深入解析达梦数据库连接管理核心机制

一、DM 监听线程基础概念

1.1 什么是 DM 监听线程

DM 监听线程是达梦数据库服务器端一个至关重要的后台线程，主要负责监听和接收客户端的连接请求。当客户端试图与达梦数据库建立通信连接时，DM 监听线程会作为第一道入口，接受连接并为其分配相应的会话资源。

在达梦数据库的线程架构中，DM 监听线程扮演着类似门卫的角色：

持续监听数据库服务端口（默认端口为 5236）
接收来自客户端的 TCP/IP 连接请求
验证客户端身份与连接参数
为成功验证的连接创建会话对象
将会话分派给工作线程进行后续处理

1.2 DM 监听线程在数据库架构中的位置

达梦数据库采用多线程架构，DM 监听线程在其中处于网络通信层与会话管理层之间，是客户端与数据库内核交互的桥梁。

#publish-mermaid-1786940978400-0{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:16px;fill:#333;}@keyframes edge-animation-frame{from{stroke-dashoffset:0;}}@keyframes dash{to{stroke-dashoffset:0;}}#publish-mermaid-1786940978400-0 .edge-animation-slow{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 50s linear infinite;stroke-linecap:round;}#publish-mermaid-1786940978400-0 .edge-animation-fast{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 20s linear infinite;stroke-linecap:round;}#publish-mermaid-1786940978400-0 .error-icon{fill:#552222;}#publish-mermaid-1786940978400-0 .error-text{fill:#552222;stroke:#552222;}#publish-mermaid-1786940978400-0 .edge-thickness-normal{stroke-width:1px;}#publish-mermaid-1786940978400-0 .edge-thickness-thick{stroke-width:3.5px;}#publish-mermaid-1786940978400-0 .edge-pattern-solid{stroke-dasharray:0;}#publish-mermaid-1786940978400-0 .edge-thickness-invisible{stroke-width:0;fill:none;}#publish-mermaid-1786940978400-0 .edge-pattern-dashed{stroke-dasharray:3;}#publish-mermaid-1786940978400-0 .edge-pattern-dotted{stroke-dasharray:2;}#publish-mermaid-1786940978400-0 .marker{fill:#333333;stroke:#333333;}#publish-mermaid-1786940978400-0 .marker.cross{stroke:#333333;}#publish-mermaid-1786940978400-0 svg{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:16px;}#publish-mermaid-1786940978400-0 p{margin:0;}#publish-mermaid-1786940978400-0 .label{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;color:#333;}#publish-mermaid-1786940978400-0 .cluster-label text{fill:#333;}#publish-mermaid-1786940978400-0 .cluster-label span{color:#333;}#publish-mermaid-1786940978400-0 .cluster-label span p{background-color:transparent;}#publish-mermaid-1786940978400-0 .label text,#publish-mermaid-1786940978400-0 span{fill:#333;color:#333;}#publish-mermaid-1786940978400-0 .node rect,#publish-mermaid-1786940978400-0 .node circle,#publish-mermaid-1786940978400-0 .node ellipse,#publish-mermaid-1786940978400-0 .node polygon,#publish-mermaid-1786940978400-0 .node path{fill:#ECECFF;stroke:#9370DB;stroke-width:1px;}#publish-mermaid-1786940978400-0 .rough-node .label text,#publish-mermaid-1786940978400-0 .node .label text,#publish-mermaid-1786940978400-0 .image-shape .label,#publish-mermaid-1786940978400-0 .icon-shape .label{text-anchor:middle;}#publish-mermaid-1786940978400-0 .node .katex path{fill:#000;stroke:#000;stroke-width:1px;}#publish-mermaid-1786940978400-0 .rough-node .label,#publish-mermaid-1786940978400-0 .node .label,#publish-mermaid-1786940978400-0 .image-shape .label,#publish-mermaid-1786940978400-0 .icon-shape .label{text-align:center;}#publish-mermaid-1786940978400-0 .node.clickable{cursor:pointer;}#publish-mermaid-1786940978400-0 .root .anchor path{fill:#333333!important;stroke-width:0;stroke:#333333;}#publish-mermaid-1786940978400-0 .arrowheadPath{fill:#333333;}#publish-mermaid-1786940978400-0 .edgePath .path{stroke:#333333;stroke-width:1px;}#publish-mermaid-1786940978400-0 .flowchart-link{stroke:#333333;fill:none;}#publish-mermaid-1786940978400-0 .edgeLabel{background-color:rgba(232,232,232, 0.8);text-align:center;}#publish-mermaid-1786940978400-0 .edgeLabel p{background-color:rgba(232,232,232, 0.8);}#publish-mermaid-1786940978400-0 .edgeLabel rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#publish-mermaid-1786940978400-0 .labelBkg{background-color:rgba(232, 232, 232, 0.5);}#publish-mermaid-1786940978400-0 .cluster rect{fill:#ffffde;stroke:#aaaa33;stroke-width:1px;}#publish-mermaid-1786940978400-0 .cluster text{fill:#333;}#publish-mermaid-1786940978400-0 .cluster span{color:#333;}#publish-mermaid-1786940978400-0 div.mermaidTooltip{position:absolute;text-align:center;max-width:200px;padding:2px;font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:12px;background:hsl(80, 100%, 96.2745098039%);border:1px solid #aaaa33;border-radius:2px;pointer-events:none;z-index:100;}#publish-mermaid-1786940978400-0 .flowchartTitleText{text-anchor:middle;font-size:18px;fill:#333;}#publish-mermaid-1786940978400-0 rect.text{fill:none;stroke-width:0;}#publish-mermaid-1786940978400-0 .icon-shape,#publish-mermaid-1786940978400-0 .image-shape{background-color:rgba(232,232,232, 0.8);text-align:center;}#publish-mermaid-1786940978400-0 .icon-shape p,#publish-mermaid-1786940978400-0 .image-shape p{background-color:rgba(232,232,232, 0.8);padding:2px;}#publish-mermaid-1786940978400-0 .icon-shape .label rect,#publish-mermaid-1786940978400-0 .image-shape .label rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#publish-mermaid-1786940978400-0 .label-icon{display:inline-block;height:1em;overflow:visible;vertical-align:-0.125em;}#publish-mermaid-1786940978400-0 .node .label-icon path{fill:currentColor;stroke:revert;stroke-width:revert;}#publish-mermaid-1786940978400-0 .node .neo-node{stroke:#9370DB;}#publish-mermaid-1786940978400-0 [data-look=\”neo\”].node rect,#publish-mermaid-1786940978400-0 [data-look=\”neo\”].cluster rect,#publish-mermaid-1786940978400-0 [data-look=\”neo\”].node polygon{stroke:#9370DB;filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978400-0 [data-look=\”neo\”].swimlane.cluster rect{filter:none;}#publish-mermaid-1786940978400-0 [data-look=\”neo\”].node path{stroke:#9370DB;stroke-width:1px;}#publish-mermaid-1786940978400-0 [data-look=\”neo\”].node .outer-path{filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978400-0 [data-look=\”neo\”].node .neo-line path{stroke:#9370DB;filter:none;}#publish-mermaid-1786940978400-0 [data-look=\”neo\”].node circle{stroke:#9370DB;filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978400-0 [data-look=\”neo\”].node circle .state-start{fill:#000000;}#publish-mermaid-1786940978400-0 [data-look=\”neo\”].icon-shape .icon{fill:#9370DB;filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978400-0 [data-look=\”neo\”].icon-shape .icon-neo path{stroke:#9370DB;filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978400-0 :root{–mermaid-font-family:\”trebuchet ms\”,verdana,arial,sans-serif;}发起 TCP 连接连接请求身份验证验证通过分派任务执行 SQL读写数据验证失败返回错误

客户端 Client

网络层

DM 监听线程

认证模块

创建会话

工作线程池

SQL 引擎

存储引擎

拒绝连接

从上图可以看出，DM 监听线程在整个数据库架构中处于关键位置，它是所有客户端连接的统一入口，直接决定了数据库的并发接入能力。

1.3 DM 监听线程的核心职责

DM 监听线程承担着以下核心职责：

1.3.1 连接监听与接收

DM 监听线程在数据库启动时绑定到指定端口，通过系统调用持续监听该端口上的连接请求。当检测到新的连接时，监听线程会调用 accept 函数接收连接，生成新的套接字描述符。

1.3.2 客户端身份验证

DM 监听线程接收到连接请求后，会与认证模块协作完成客户端身份验证，包括：

用户名与密码校验
客户端 IP 地址白名单检查
连接加密协议协商
资源配额验证

1.3.3 会话创建与管理

验证通过后，DM 监听线程会为该连接创建一个会话对象，会话对象包含了客户端连接的所有上下文信息，如事务状态、权限信息、临时表空间等。

1.3.4 任务分派

DM 监听线程创建会话后，会将该会话分派给工作线程池中的空闲工作线程，由工作线程负责后续的 SQL 解析、执行与结果返回。

二、DM 监听线程的工作原理

2.1 DM 监听线程的启动流程

DM 监听线程的启动是数据库服务器启动过程中的重要环节，其启动流程如下：

#publish-mermaid-1786940978458-1{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:16px;fill:#333;}@keyframes edge-animation-frame{from{stroke-dashoffset:0;}}@keyframes dash{to{stroke-dashoffset:0;}}#publish-mermaid-1786940978458-1 .edge-animation-slow{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 50s linear infinite;stroke-linecap:round;}#publish-mermaid-1786940978458-1 .edge-animation-fast{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 20s linear infinite;stroke-linecap:round;}#publish-mermaid-1786940978458-1 .error-icon{fill:#552222;}#publish-mermaid-1786940978458-1 .error-text{fill:#552222;stroke:#552222;}#publish-mermaid-1786940978458-1 .edge-thickness-normal{stroke-width:1px;}#publish-mermaid-1786940978458-1 .edge-thickness-thick{stroke-width:3.5px;}#publish-mermaid-1786940978458-1 .edge-pattern-solid{stroke-dasharray:0;}#publish-mermaid-1786940978458-1 .edge-thickness-invisible{stroke-width:0;fill:none;}#publish-mermaid-1786940978458-1 .edge-pattern-dashed{stroke-dasharray:3;}#publish-mermaid-1786940978458-1 .edge-pattern-dotted{stroke-dasharray:2;}#publish-mermaid-1786940978458-1 .marker{fill:#333333;stroke:#333333;}#publish-mermaid-1786940978458-1 .marker.cross{stroke:#333333;}#publish-mermaid-1786940978458-1 svg{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:16px;}#publish-mermaid-1786940978458-1 p{margin:0;}#publish-mermaid-1786940978458-1 .label{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;color:#333;}#publish-mermaid-1786940978458-1 .cluster-label text{fill:#333;}#publish-mermaid-1786940978458-1 .cluster-label span{color:#333;}#publish-mermaid-1786940978458-1 .cluster-label span p{background-color:transparent;}#publish-mermaid-1786940978458-1 .label text,#publish-mermaid-1786940978458-1 span{fill:#333;color:#333;}#publish-mermaid-1786940978458-1 .node rect,#publish-mermaid-1786940978458-1 .node circle,#publish-mermaid-1786940978458-1 .node ellipse,#publish-mermaid-1786940978458-1 .node polygon,#publish-mermaid-1786940978458-1 .node path{fill:#ECECFF;stroke:#9370DB;stroke-width:1px;}#publish-mermaid-1786940978458-1 .rough-node .label text,#publish-mermaid-1786940978458-1 .node .label text,#publish-mermaid-1786940978458-1 .image-shape .label,#publish-mermaid-1786940978458-1 .icon-shape .label{text-anchor:middle;}#publish-mermaid-1786940978458-1 .node .katex path{fill:#000;stroke:#000;stroke-width:1px;}#publish-mermaid-1786940978458-1 .rough-node .label,#publish-mermaid-1786940978458-1 .node .label,#publish-mermaid-1786940978458-1 .image-shape .label,#publish-mermaid-1786940978458-1 .icon-shape .label{text-align:center;}#publish-mermaid-1786940978458-1 .node.clickable{cursor:pointer;}#publish-mermaid-1786940978458-1 .root .anchor path{fill:#333333!important;stroke-width:0;stroke:#333333;}#publish-mermaid-1786940978458-1 .arrowheadPath{fill:#333333;}#publish-mermaid-1786940978458-1 .edgePath .path{stroke:#333333;stroke-width:1px;}#publish-mermaid-1786940978458-1 .flowchart-link{stroke:#333333;fill:none;}#publish-mermaid-1786940978458-1 .edgeLabel{background-color:rgba(232,232,232, 0.8);text-align:center;}#publish-mermaid-1786940978458-1 .edgeLabel p{background-color:rgba(232,232,232, 0.8);}#publish-mermaid-1786940978458-1 .edgeLabel rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#publish-mermaid-1786940978458-1 .labelBkg{background-color:rgba(232, 232, 232, 0.5);}#publish-mermaid-1786940978458-1 .cluster rect{fill:#ffffde;stroke:#aaaa33;stroke-width:1px;}#publish-mermaid-1786940978458-1 .cluster text{fill:#333;}#publish-mermaid-1786940978458-1 .cluster span{color:#333;}#publish-mermaid-1786940978458-1 div.mermaidTooltip{position:absolute;text-align:center;max-width:200px;padding:2px;font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:12px;background:hsl(80, 100%, 96.2745098039%);border:1px solid #aaaa33;border-radius:2px;pointer-events:none;z-index:100;}#publish-mermaid-1786940978458-1 .flowchartTitleText{text-anchor:middle;font-size:18px;fill:#333;}#publish-mermaid-1786940978458-1 rect.text{fill:none;stroke-width:0;}#publish-mermaid-1786940978458-1 .icon-shape,#publish-mermaid-1786940978458-1 .image-shape{background-color:rgba(232,232,232, 0.8);text-align:center;}#publish-mermaid-1786940978458-1 .icon-shape p,#publish-mermaid-1786940978458-1 .image-shape p{background-color:rgba(232,232,232, 0.8);padding:2px;}#publish-mermaid-1786940978458-1 .icon-shape .label rect,#publish-mermaid-1786940978458-1 .image-shape .label rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#publish-mermaid-1786940978458-1 .label-icon{display:inline-block;height:1em;overflow:visible;vertical-align:-0.125em;}#publish-mermaid-1786940978458-1 .node .label-icon path{fill:currentColor;stroke:revert;stroke-width:revert;}#publish-mermaid-1786940978458-1 .node .neo-node{stroke:#9370DB;}#publish-mermaid-1786940978458-1 [data-look=\”neo\”].node rect,#publish-mermaid-1786940978458-1 [data-look=\”neo\”].cluster rect,#publish-mermaid-1786940978458-1 [data-look=\”neo\”].node polygon{stroke:#9370DB;filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978458-1 [data-look=\”neo\”].swimlane.cluster rect{filter:none;}#publish-mermaid-1786940978458-1 [data-look=\”neo\”].node path{stroke:#9370DB;stroke-width:1px;}#publish-mermaid-1786940978458-1 [data-look=\”neo\”].node .outer-path{filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978458-1 [data-look=\”neo\”].node .neo-line path{stroke:#9370DB;filter:none;}#publish-mermaid-1786940978458-1 [data-look=\”neo\”].node circle{stroke:#9370DB;filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978458-1 [data-look=\”neo\”].node circle .state-start{fill:#000000;}#publish-mermaid-1786940978458-1 [data-look=\”neo\”].icon-shape .icon{fill:#9370DB;filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978458-1 [data-look=\”neo\”].icon-shape .icon-neo path{stroke:#9370DB;filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978458-1 :root{–mermaid-font-family:\”trebuchet ms\”,verdana,arial,sans-serif;}成功失败

数据库服务器启动

读取 dm.ini 配置文件

解析网络相关参数

创建监听套接字

绑定 IP 地址与端口

绑定是否成功

调用 listen 开始监听

输出错误日志

服务器启动失败

创建 DM 监听线程

进入事件循环

等待客户端连接

2.1.1 配置参数加载

在启动阶段，数据库会从 dm.ini 配置文件中加载与监听相关的关键参数：

| 参数名 | 说明 | 默认值 |

|——–|——|——–|

| PORT_NUM | 监听端口号 | 5236 |

| LISTEN_IP | 监听 IP 地址 | 0.0.0.0 |

| MAX_SESSIONS | 最大会话数 | 1000 |

| SSL_HOSTNAME | SSL 主机名 | 无 |

| ENABLE_ENCRYPT | 是否启用加密 | 0 |

2.1.2 套接字创建与绑定

DM 监听线程启动时会执行以下系统调用序列：

调用 socket() 创建 TCP 套接字

设置 SO_REUSEADDR 选项，允许端口复用

调用 bind() 将套接字绑定到指定 IP 和端口

调用 listen() 开始监听，设置等待队列长度

注册到 I/O 多路复用机制（如 epoll）

2.2 DM 监听线程的连接处理机制

DM 监听线程采用事件驱动的连接处理机制，核心流程如下：

#publish-mermaid-1786940978760-2{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:16px;fill:#333;}@keyframes edge-animation-frame{from{stroke-dashoffset:0;}}@keyframes dash{to{stroke-dashoffset:0;}}#publish-mermaid-1786940978760-2 .edge-animation-slow{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 50s linear infinite;stroke-linecap:round;}#publish-mermaid-1786940978760-2 .edge-animation-fast{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 20s linear infinite;stroke-linecap:round;}#publish-mermaid-1786940978760-2 .error-icon{fill:#552222;}#publish-mermaid-1786940978760-2 .error-text{fill:#552222;stroke:#552222;}#publish-mermaid-1786940978760-2 .edge-thickness-normal{stroke-width:1px;}#publish-mermaid-1786940978760-2 .edge-thickness-thick{stroke-width:3.5px;}#publish-mermaid-1786940978760-2 .edge-pattern-solid{stroke-dasharray:0;}#publish-mermaid-1786940978760-2 .edge-thickness-invisible{stroke-width:0;fill:none;}#publish-mermaid-1786940978760-2 .edge-pattern-dashed{stroke-dasharray:3;}#publish-mermaid-1786940978760-2 .edge-pattern-dotted{stroke-dasharray:2;}#publish-mermaid-1786940978760-2 .marker{fill:#333333;stroke:#333333;}#publish-mermaid-1786940978760-2 .marker.cross{stroke:#333333;}#publish-mermaid-1786940978760-2 svg{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:16px;}#publish-mermaid-1786940978760-2 p{margin:0;}#publish-mermaid-1786940978760-2 .label{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;color:#333;}#publish-mermaid-1786940978760-2 .cluster-label text{fill:#333;}#publish-mermaid-1786940978760-2 .cluster-label span{color:#333;}#publish-mermaid-1786940978760-2 .cluster-label span p{background-color:transparent;}#publish-mermaid-1786940978760-2 .label text,#publish-mermaid-1786940978760-2 span{fill:#333;color:#333;}#publish-mermaid-1786940978760-2 .node rect,#publish-mermaid-1786940978760-2 .node circle,#publish-mermaid-1786940978760-2 .node ellipse,#publish-mermaid-1786940978760-2 .node polygon,#publish-mermaid-1786940978760-2 .node path{fill:#ECECFF;stroke:#9370DB;stroke-width:1px;}#publish-mermaid-1786940978760-2 .rough-node .label text,#publish-mermaid-1786940978760-2 .node .label text,#publish-mermaid-1786940978760-2 .image-shape .label,#publish-mermaid-1786940978760-2 .icon-shape .label{text-anchor:middle;}#publish-mermaid-1786940978760-2 .node .katex path{fill:#000;stroke:#000;stroke-width:1px;}#publish-mermaid-1786940978760-2 .rough-node .label,#publish-mermaid-1786940978760-2 .node .label,#publish-mermaid-1786940978760-2 .image-shape .label,#publish-mermaid-1786940978760-2 .icon-shape .label{text-align:center;}#publish-mermaid-1786940978760-2 .node.clickable{cursor:pointer;}#publish-mermaid-1786940978760-2 .root .anchor path{fill:#333333!important;stroke-width:0;stroke:#333333;}#publish-mermaid-1786940978760-2 .arrowheadPath{fill:#333333;}#publish-mermaid-1786940978760-2 .edgePath .path{stroke:#333333;stroke-width:1px;}#publish-mermaid-1786940978760-2 .flowchart-link{stroke:#333333;fill:none;}#publish-mermaid-1786940978760-2 .edgeLabel{background-color:rgba(232,232,232, 0.8);text-align:center;}#publish-mermaid-1786940978760-2 .edgeLabel p{background-color:rgba(232,232,232, 0.8);}#publish-mermaid-1786940978760-2 .edgeLabel rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#publish-mermaid-1786940978760-2 .labelBkg{background-color:rgba(232, 232, 232, 0.5);}#publish-mermaid-1786940978760-2 .cluster rect{fill:#ffffde;stroke:#aaaa33;stroke-width:1px;}#publish-mermaid-1786940978760-2 .cluster text{fill:#333;}#publish-mermaid-1786940978760-2 .cluster span{color:#333;}#publish-mermaid-1786940978760-2 div.mermaidTooltip{position:absolute;text-align:center;max-width:200px;padding:2px;font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:12px;background:hsl(80, 100%, 96.2745098039%);border:1px solid #aaaa33;border-radius:2px;pointer-events:none;z-index:100;}#publish-mermaid-1786940978760-2 .flowchartTitleText{text-anchor:middle;font-size:18px;fill:#333;}#publish-mermaid-1786940978760-2 rect.text{fill:none;stroke-width:0;}#publish-mermaid-1786940978760-2 .icon-shape,#publish-mermaid-1786940978760-2 .image-shape{background-color:rgba(232,232,232, 0.8);text-align:center;}#publish-mermaid-1786940978760-2 .icon-shape p,#publish-mermaid-1786940978760-2 .image-shape p{background-color:rgba(232,232,232, 0.8);padding:2px;}#publish-mermaid-1786940978760-2 .icon-shape .label rect,#publish-mermaid-1786940978760-2 .image-shape .label rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#publish-mermaid-1786940978760-2 .label-icon{display:inline-block;height:1em;overflow:visible;vertical-align:-0.125em;}#publish-mermaid-1786940978760-2 .node .label-icon path{fill:currentColor;stroke:revert;stroke-width:revert;}#publish-mermaid-1786940978760-2 .node .neo-node{stroke:#9370DB;}#publish-mermaid-1786940978760-2 [data-look=\”neo\”].node rect,#publish-mermaid-1786940978760-2 [data-look=\”neo\”].cluster rect,#publish-mermaid-1786940978760-2 [data-look=\”neo\”].node polygon{stroke:#9370DB;filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978760-2 [data-look=\”neo\”].swimlane.cluster rect{filter:none;}#publish-mermaid-1786940978760-2 [data-look=\”neo\”].node path{stroke:#9370DB;stroke-width:1px;}#publish-mermaid-1786940978760-2 [data-look=\”neo\”].node .outer-path{filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978760-2 [data-look=\”neo\”].node .neo-line path{stroke:#9370DB;filter:none;}#publish-mermaid-1786940978760-2 [data-look=\”neo\”].node circle{stroke:#9370DB;filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978760-2 [data-look=\”neo\”].node circle .state-start{fill:#000000;}#publish-mermaid-1786940978760-2 [data-look=\”neo\”].icon-shape .icon{fill:#9370DB;filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978760-2 [data-look=\”neo\”].icon-shape .icon-neo path{stroke:#9370DB;filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978760-2 :root{–mermaid-font-family:\”trebuchet ms\”,verdana,arial,sans-serif;}是否成功失败

DM 监听线程运行中

epoll_wait 等待事件

是否有新连接

调用 accept 接收连接

获取客户端套接字 fd

读取连接握手包

解析客户端协议版本

执行身份认证

认证是否成功

分配会话 ID

发送错误响应

关闭客户端套接字

创建会话对象

分派给工作线程

2.2.1 I/O 多路复用模型

DM 监听线程在 Linux 系统上默认使用 epoll 作为 I/O 多路复用机制，具有以下优势：

支持大量并发连接（C10K 甚至更高）
事件触发机制，无需轮询
O(1) 时间复杂度的事件通知
支持边缘触发与水平触发两种模式

2.2.2 连接握手过程

当 DM 监听线程接收到新连接后，会执行完整的握手协议：

— 查看当前连接信息
SELECT
SESS_ID,
SQL_TEXT,
STATE,
CREATE_TIME,
CLNT_IP
FROM V$SESSIONS
WHERE STATE = 'ACTIVE';

上述 SQL 可以查看当前活跃的数据库会话信息，包括会话 ID、客户端 IP 和创建时间等。

2.3 DM 监听线程与会话管理

DM 监听线程与会话管理紧密关联，其协作机制如下：

#publish-mermaid-1786940978843-3{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:16px;fill:#333;}@keyframes edge-animation-frame{from{stroke-dashoffset:0;}}@keyframes dash{to{stroke-dashoffset:0;}}#publish-mermaid-1786940978843-3 .edge-animation-slow{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 50s linear infinite;stroke-linecap:round;}#publish-mermaid-1786940978843-3 .edge-animation-fast{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 20s linear infinite;stroke-linecap:round;}#publish-mermaid-1786940978843-3 .error-icon{fill:#552222;}#publish-mermaid-1786940978843-3 .error-text{fill:#552222;stroke:#552222;}#publish-mermaid-1786940978843-3 .edge-thickness-normal{stroke-width:1px;}#publish-mermaid-1786940978843-3 .edge-thickness-thick{stroke-width:3.5px;}#publish-mermaid-1786940978843-3 .edge-pattern-solid{stroke-dasharray:0;}#publish-mermaid-1786940978843-3 .edge-thickness-invisible{stroke-width:0;fill:none;}#publish-mermaid-1786940978843-3 .edge-pattern-dashed{stroke-dasharray:3;}#publish-mermaid-1786940978843-3 .edge-pattern-dotted{stroke-dasharray:2;}#publish-mermaid-1786940978843-3 .marker{fill:#333333;stroke:#333333;}#publish-mermaid-1786940978843-3 .marker.cross{stroke:#333333;}#publish-mermaid-1786940978843-3 svg{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:16px;}#publish-mermaid-1786940978843-3 p{margin:0;}#publish-mermaid-1786940978843-3 .label{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;color:#333;}#publish-mermaid-1786940978843-3 .cluster-label text{fill:#333;}#publish-mermaid-1786940978843-3 .cluster-label span{color:#333;}#publish-mermaid-1786940978843-3 .cluster-label span p{background-color:transparent;}#publish-mermaid-1786940978843-3 .label text,#publish-mermaid-1786940978843-3 span{fill:#333;color:#333;}#publish-mermaid-1786940978843-3 .node rect,#publish-mermaid-1786940978843-3 .node circle,#publish-mermaid-1786940978843-3 .node ellipse,#publish-mermaid-1786940978843-3 .node polygon,#publish-mermaid-1786940978843-3 .node path{fill:#ECECFF;stroke:#9370DB;stroke-width:1px;}#publish-mermaid-1786940978843-3 .rough-node .label text,#publish-mermaid-1786940978843-3 .node .label text,#publish-mermaid-1786940978843-3 .image-shape .label,#publish-mermaid-1786940978843-3 .icon-shape .label{text-anchor:middle;}#publish-mermaid-1786940978843-3 .node .katex path{fill:#000;stroke:#000;stroke-width:1px;}#publish-mermaid-1786940978843-3 .rough-node .label,#publish-mermaid-1786940978843-3 .node .label,#publish-mermaid-1786940978843-3 .image-shape .label,#publish-mermaid-1786940978843-3 .icon-shape .label{text-align:center;}#publish-mermaid-1786940978843-3 .node.clickable{cursor:pointer;}#publish-mermaid-1786940978843-3 .root .anchor path{fill:#333333!important;stroke-width:0;stroke:#333333;}#publish-mermaid-1786940978843-3 .arrowheadPath{fill:#333333;}#publish-mermaid-1786940978843-3 .edgePath .path{stroke:#333333;stroke-width:1px;}#publish-mermaid-1786940978843-3 .flowchart-link{stroke:#333333;fill:none;}#publish-mermaid-1786940978843-3 .edgeLabel{background-color:rgba(232,232,232, 0.8);text-align:center;}#publish-mermaid-1786940978843-3 .edgeLabel p{background-color:rgba(232,232,232, 0.8);}#publish-mermaid-1786940978843-3 .edgeLabel rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#publish-mermaid-1786940978843-3 .labelBkg{background-color:rgba(232, 232, 232, 0.5);}#publish-mermaid-1786940978843-3 .cluster rect{fill:#ffffde;stroke:#aaaa33;stroke-width:1px;}#publish-mermaid-1786940978843-3 .cluster text{fill:#333;}#publish-mermaid-1786940978843-3 .cluster span{color:#333;}#publish-mermaid-1786940978843-3 div.mermaidTooltip{position:absolute;text-align:center;max-width:200px;padding:2px;font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:12px;background:hsl(80, 100%, 96.2745098039%);border:1px solid #aaaa33;border-radius:2px;pointer-events:none;z-index:100;}#publish-mermaid-1786940978843-3 .flowchartTitleText{text-anchor:middle;font-size:18px;fill:#333;}#publish-mermaid-1786940978843-3 rect.text{fill:none;stroke-width:0;}#publish-mermaid-1786940978843-3 .icon-shape,#publish-mermaid-1786940978843-3 .image-shape{background-color:rgba(232,232,232, 0.8);text-align:center;}#publish-mermaid-1786940978843-3 .icon-shape p,#publish-mermaid-1786940978843-3 .image-shape p{background-color:rgba(232,232,232, 0.8);padding:2px;}#publish-mermaid-1786940978843-3 .icon-shape .label rect,#publish-mermaid-1786940978843-3 .image-shape .label rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#publish-mermaid-1786940978843-3 .label-icon{display:inline-block;height:1em;overflow:visible;vertical-align:-0.125em;}#publish-mermaid-1786940978843-3 .node .label-icon path{fill:currentColor;stroke:revert;stroke-width:revert;}#publish-mermaid-1786940978843-3 .node .neo-node{stroke:#9370DB;}#publish-mermaid-1786940978843-3 [data-look=\”neo\”].node rect,#publish-mermaid-1786940978843-3 [data-look=\”neo\”].cluster rect,#publish-mermaid-1786940978843-3 [data-look=\”neo\”].node polygon{stroke:#9370DB;filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978843-3 [data-look=\”neo\”].swimlane.cluster rect{filter:none;}#publish-mermaid-1786940978843-3 [data-look=\”neo\”].node path{stroke:#9370DB;stroke-width:1px;}#publish-mermaid-1786940978843-3 [data-look=\”neo\”].node .outer-path{filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978843-3 [data-look=\”neo\”].node .neo-line path{stroke:#9370DB;filter:none;}#publish-mermaid-1786940978843-3 [data-look=\”neo\”].node circle{stroke:#9370DB;filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978843-3 [data-look=\”neo\”].node circle .state-start{fill:#000000;}#publish-mermaid-1786940978843-3 [data-look=\”neo\”].icon-shape .icon{fill:#9370DB;filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978843-3 [data-look=\”neo\”].icon-shape .icon-neo path{stroke:#9370DB;filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978843-3 :root{–mermaid-font-family:\”trebuchet ms\”,verdana,arial,sans-serif;}执行层会话管理层监听层创建会话分配分配分配会话结束会话结束会话结束回收资源

DM 监听线程

会话池

会话回收器

工作线程 1

工作线程 2

工作线程 N

2.3.1 会话生命周期管理

每个通过 DM 监听线程创建的会话都有完整的生命周期：

创建阶段：DM 监听线程分配会话 ID 和内存结构

活跃阶段：工作线程处理客户端请求

空闲阶段：会话保持连接但无活跃请求

终止阶段：客户端断开或超时，会话资源被回收

2.3.2 会话池机制

达梦数据库采用会话池机制提高性能，DM 监听线程创建会话时会优先从会话池中复用已有结构：

— 查看会话池状态
SELECT
NAME,
POOL_SIZE,
USED_COUNT,
FREE_COUNT
FROM V$POOL;

三、DM 监听线程的配置与调优

3.1 DM 监听线程相关参数配置

合理配置 DM 监听线程相关参数对数据库性能至关重要，以下是关键参数详解：

3.1.1 网络监听参数配置

在 dm.ini 配置文件中，与 DM 监听线程直接相关的参数如下：

# 监听端口号
PORT_NUM = 5236

# 监听 IP 地址，0.0.0.0 表示监听所有网卡
LISTEN_IP = 0.0.0.0

# 最大并发会话数
MAX_SESSIONS = 1000

# 最大会话数达到后的处理策略
MAX_SESSION_POLICY = 0

# 会话超时时间（秒）
SESSION_TIMEOUT = 60

# TCP keepalive 探测间隔（秒）
TCP_KEEPALIVE_INTERVAL = 30

3.1.2 连接安全参数配置

# 启用 SSL 加密
ENABLE_ENCRYPT = 1

# SSL 证书路径
SSL_CERT_PATH = /dm8/data/ssl/server.crt

# SSL 私钥路径
SSL_KEY_PATH = /dm8/data/ssl/server.key

# 允许的 IP 地址列表
IP_CONTROL = 1
IP_CONTROL_FILE = /dm8/data/ip_control.txt

3.1.3 参数动态修改

部分参数支持在线动态修改，无需重启数据库：

— 动态修改最大会话数
CALL SP_SET_PARA_VALUE(2, 'MAX_SESSIONS', 2000);

— 查看参数当前值
SELECT
PARA_NAME,
PARA_VALUE,
READ_ONLY
FROM V$DM_INI
WHERE PARA_NAME IN ('PORT_NUM', 'MAX_SESSIONS', 'SESSION_TIMEOUT');

3.2 DM 监听线程的性能监控

3.2.1 监控连接数指标

通过系统视图监控 DM 监听线程的运行状态：

— 查看当前连接数统计
SELECT
COUNT(*) AS TOTAL_SESSIONS,
SUM(CASE WHEN STATE = 'ACTIVE' THEN 1 ELSE 0 END) AS ACTIVE_SESSIONS,
SUM(CASE WHEN STATE = 'IDLE' THEN 1 ELSE 0 END) AS IDLE_SESSIONS,
COUNT(DISTINCT CLNT_IP) AS UNIQUE_IPS
FROM V$SESSIONS;

3.2.2 监控线程状态

— 查看 DM 监听线程运行状态
SELECT
ID AS THREAD_ID,
NAME AS THREAD_NAME,
THREAD_DESC,
CREATE_TIME
FROM V$THREADS
WHERE NAME LIKE '%LISTEN%';

3.2.3 连接历史趋势分析

— 查看近期连接创建情况
SELECT
TO_CHAR(CREATE_TIME, 'YYYY-MM-DD HH24') AS HOUR,
COUNT(*) AS CONN_COUNT,
COUNT(DISTINCT CLNT_IP) AS UNIQUE_IPS
FROM V$SESSIONS
WHERE CREATE_TIME >= SYSDATE – 1
GROUP BY TO_CHAR(CREATE_TIME, 'YYYY-MM-DD HH24')
ORDER BY HOUR DESC;

3.2.4 操作系统层面监控

在 Linux 系统中，可以使用以下命令监控 DM 监听线程的网络连接状态：

# 查看数据库监听端口连接状态统计
netstat -an | grep 5236 | awk '{print $6}' | sort | uniq -c | sort -rn

# 查看监听线程进程信息
ps -ef | grep dmserver | grep -v grep

# 使用 ss 命令查看监听套接字
ss -tlnp | grep 5236

3.3 DM 监听线程的常见问题排查

3.3.1 连接被拒绝问题

当客户端无法连接数据库时，排查流程如下：

#publish-mermaid-1786940978904-4{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:16px;fill:#333;}@keyframes edge-animation-frame{from{stroke-dashoffset:0;}}@keyframes dash{to{stroke-dashoffset:0;}}#publish-mermaid-1786940978904-4 .edge-animation-slow{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 50s linear infinite;stroke-linecap:round;}#publish-mermaid-1786940978904-4 .edge-animation-fast{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 20s linear infinite;stroke-linecap:round;}#publish-mermaid-1786940978904-4 .error-icon{fill:#552222;}#publish-mermaid-1786940978904-4 .error-text{fill:#552222;stroke:#552222;}#publish-mermaid-1786940978904-4 .edge-thickness-normal{stroke-width:1px;}#publish-mermaid-1786940978904-4 .edge-thickness-thick{stroke-width:3.5px;}#publish-mermaid-1786940978904-4 .edge-pattern-solid{stroke-dasharray:0;}#publish-mermaid-1786940978904-4 .edge-thickness-invisible{stroke-width:0;fill:none;}#publish-mermaid-1786940978904-4 .edge-pattern-dashed{stroke-dasharray:3;}#publish-mermaid-1786940978904-4 .edge-pattern-dotted{stroke-dasharray:2;}#publish-mermaid-1786940978904-4 .marker{fill:#333333;stroke:#333333;}#publish-mermaid-1786940978904-4 .marker.cross{stroke:#333333;}#publish-mermaid-1786940978904-4 svg{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:16px;}#publish-mermaid-1786940978904-4 p{margin:0;}#publish-mermaid-1786940978904-4 .label{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;color:#333;}#publish-mermaid-1786940978904-4 .cluster-label text{fill:#333;}#publish-mermaid-1786940978904-4 .cluster-label span{color:#333;}#publish-mermaid-1786940978904-4 .cluster-label span p{background-color:transparent;}#publish-mermaid-1786940978904-4 .label text,#publish-mermaid-1786940978904-4 span{fill:#333;color:#333;}#publish-mermaid-1786940978904-4 .node rect,#publish-mermaid-1786940978904-4 .node circle,#publish-mermaid-1786940978904-4 .node ellipse,#publish-mermaid-1786940978904-4 .node polygon,#publish-mermaid-1786940978904-4 .node path{fill:#ECECFF;stroke:#9370DB;stroke-width:1px;}#publish-mermaid-1786940978904-4 .rough-node .label text,#publish-mermaid-1786940978904-4 .node .label text,#publish-mermaid-1786940978904-4 .image-shape .label,#publish-mermaid-1786940978904-4 .icon-shape .label{text-anchor:middle;}#publish-mermaid-1786940978904-4 .node .katex path{fill:#000;stroke:#000;stroke-width:1px;}#publish-mermaid-1786940978904-4 .rough-node .label,#publish-mermaid-1786940978904-4 .node .label,#publish-mermaid-1786940978904-4 .image-shape .label,#publish-mermaid-1786940978904-4 .icon-shape .label{text-align:center;}#publish-mermaid-1786940978904-4 .node.clickable{cursor:pointer;}#publish-mermaid-1786940978904-4 .root .anchor path{fill:#333333!important;stroke-width:0;stroke:#333333;}#publish-mermaid-1786940978904-4 .arrowheadPath{fill:#333333;}#publish-mermaid-1786940978904-4 .edgePath .path{stroke:#333333;stroke-width:1px;}#publish-mermaid-1786940978904-4 .flowchart-link{stroke:#333333;fill:none;}#publish-mermaid-1786940978904-4 .edgeLabel{background-color:rgba(232,232,232, 0.8);text-align:center;}#publish-mermaid-1786940978904-4 .edgeLabel p{background-color:rgba(232,232,232, 0.8);}#publish-mermaid-1786940978904-4 .edgeLabel rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#publish-mermaid-1786940978904-4 .labelBkg{background-color:rgba(232, 232, 232, 0.5);}#publish-mermaid-1786940978904-4 .cluster rect{fill:#ffffde;stroke:#aaaa33;stroke-width:1px;}#publish-mermaid-1786940978904-4 .cluster text{fill:#333;}#publish-mermaid-1786940978904-4 .cluster span{color:#333;}#publish-mermaid-1786940978904-4 div.mermaidTooltip{position:absolute;text-align:center;max-width:200px;padding:2px;font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:12px;background:hsl(80, 100%, 96.2745098039%);border:1px solid #aaaa33;border-radius:2px;pointer-events:none;z-index:100;}#publish-mermaid-1786940978904-4 .flowchartTitleText{text-anchor:middle;font-size:18px;fill:#333;}#publish-mermaid-1786940978904-4 rect.text{fill:none;stroke-width:0;}#publish-mermaid-1786940978904-4 .icon-shape,#publish-mermaid-1786940978904-4 .image-shape{background-color:rgba(232,232,232, 0.8);text-align:center;}#publish-mermaid-1786940978904-4 .icon-shape p,#publish-mermaid-1786940978904-4 .image-shape p{background-color:rgba(232,232,232, 0.8);padding:2px;}#publish-mermaid-1786940978904-4 .icon-shape .label rect,#publish-mermaid-1786940978904-4 .image-shape .label rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#publish-mermaid-1786940978904-4 .label-icon{display:inline-block;height:1em;overflow:visible;vertical-align:-0.125em;}#publish-mermaid-1786940978904-4 .node .label-icon path{fill:currentColor;stroke:revert;stroke-width:revert;}#publish-mermaid-1786940978904-4 .node .neo-node{stroke:#9370DB;}#publish-mermaid-1786940978904-4 [data-look=\”neo\”].node rect,#publish-mermaid-1786940978904-4 [data-look=\”neo\”].cluster rect,#publish-mermaid-1786940978904-4 [data-look=\”neo\”].node polygon{stroke:#9370DB;filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978904-4 [data-look=\”neo\”].swimlane.cluster rect{filter:none;}#publish-mermaid-1786940978904-4 [data-look=\”neo\”].node path{stroke:#9370DB;stroke-width:1px;}#publish-mermaid-1786940978904-4 [data-look=\”neo\”].node .outer-path{filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978904-4 [data-look=\”neo\”].node .neo-line path{stroke:#9370DB;filter:none;}#publish-mermaid-1786940978904-4 [data-look=\”neo\”].node circle{stroke:#9370DB;filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978904-4 [data-look=\”neo\”].node circle .state-start{fill:#000000;}#publish-mermaid-1786940978904-4 [data-look=\”neo\”].icon-shape .icon{fill:#9370DB;filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978904-4 [data-look=\”neo\”].icon-shape .icon-neo path{stroke:#9370DB;filter:drop-shadow(1px 2px 2px rgba(185, 185, 185, 1));}#publish-mermaid-1786940978904-4 :root{–mermaid-font-family:\”trebuchet ms\”,verdana,arial,sans-serif;}未启动已启动未监听已监听未放行已放行被限制未限制达到上限未达上限

客户端连接失败

数据库是否启动

启动数据库服务

端口是否监听

检查 dm.ini 配置

防火墙是否放行

配置防火墙规则

IP 白名单是否限制

添加客户端 IP 到白名单

会话数是否达上限

调整 MAX_SESSIONS

检查认证日志

联系 DBA 进一步排查

问题排查步骤：

检查数据库服务状态：

# 检查 dmserver 进程
ps -ef | grep dmserver

# 检查端口监听状态
netstat -tlnp | grep 5236

检查防火墙配置：

# 查看 iptables 规则
iptables -L -n | grep 5236

# 开放端口
firewall-cmd –add-port=5236/tcp –permanent
firewall-cmd –reload

检查 IP 访问控制：

— 查看 IP 控制配置
SELECT * FROM V$DM_INI WHERE PARA_NAME = 'IP_CONTROL';

3.3.2 连接数过高问题

当数据库连接数异常升高时，可以执行以下排查与处理步骤：

— 步骤 1：查看连接数最高的客户端 IP
SELECT
CLNT_IP,
COUNT(*) AS CONN_COUNT
FROM V$SESSIONS
GROUP BY CLNT_IP
ORDER BY CONN_COUNT DESC
FETCH FIRST 10 ROWS ONLY;

— 步骤 2：查看长时间运行的会话
SELECT
SESS_ID,
CLNT_IP,
SQL_TEXT,
CREATE_TIME,
LAST_RECV_TIME
FROM V$SESSIONS
WHERE STATE = 'ACTIVE'
AND CREATE_TIME < SYSDATE – 1/24
ORDER BY CREATE_TIME;

— 步骤 3：终止异常会话
CALL SP_CLOSE_SESSION(会话ID);

3.3.3 监听线程性能优化建议

针对 DM 监听线程的性能优化，建议从以下方面入手：

合理设置 MAX_SESSIONS 参数，避免过大导致内存压力

启用连接池中间件，减少频繁建立连接的开销

配置会话超时时间，及时回收空闲会话

启用 SSL 加密时注意 CPU 开销，必要时使用硬件加速

定期监控连接趋势，提前进行容量规划

配置 IP 白名单，减少非法连接尝试的资源消耗

— 优化后的参数配置示例
CALL SP_SET_PARA_VALUE(2, 'MAX_SESSIONS', 1500);
CALL SP_SET_PARA_VALUE(2, 'SESSION_TIMEOUT', 120);
CALL SP_SET_PARA_VALUE(2, 'TCP_KEEPALIVE_INTERVAL', 60);

通过以上配置与监控措施，可以确保 DM 监听线程高效稳定运行，为达梦数据库提供可靠的连接管理服务。在实际运维中，建议结合业务特点持续优化参数配置，建立完善的监控告警机制，及时发现并处理连接异常问题。