impact-analysis

变更影响分析

概述

影响分析用于确定 CI 变更会影响哪些内容。本技能涵盖：

• 使用 CMDB 关系追踪影响路径
• 识别受影响的业务服务
• 将 CI 关键性映射为业务影响
• 根据 CI 关系量化变更风险
• 生成供 CAB 审核的影响报告

**使用时机：**实施变更前、事件分类期间、容量规划时，或评估新部署时。

**价值主张：**准确的影响分析可避免意外停机、减少变更失败，并支持知情的风险决策。

前提条件

• **角色：**具有 itil、change_manager 或 cmdb_read 访问权限
• **访问权限：**cmdb_ci、cmdb_rel_ci、cmdb_ci_service、service_ci_assoc 表
• **知识：**CMDB 关系、服务映射概念
• **相关技能：**先完成 cmdb/relationship-mapping

操作流程

步骤 1：确定要变更的 CI

首先，找到将受变更影响的 CI：

按名称搜索：

Tool: SN-Query-Table
Parameters:
  table_name: cmdb_ci
  query: nameLIKEprod-web-01
  fields: sys_id,name,sys_class_name,operational_status,business_criticality

按 IP 地址搜索：

Tool: SN-Query-Table
Parameters:
  table_name: cmdb_ci_computer
  query: ip_address=10.0.1.100
  fields: sys_id,name,sys_class_name,operational_status,support_group

使用便捷工具：

Tool: SN-List-CmdbCis
Parameters:
  ci_class: cmdb_ci_server
  query: name=prod-web-01
  fields: sys_id,name,business_criticality,support_group

步骤 2：映射上游影响（哪些内容依赖此 CI）

追踪依赖于要变更 CI 的内容：

直接依赖（1 层）：

Tool: SN-Query-Table
Parameters:
  table_name: cmdb_rel_ci
  query: child=[ci_sys_id]^type.parent_descriptorLIKEDepends
  fields: parent,parent.name,parent.sys_class_name,type.parent_descriptor

获取依赖 CI 的详细信息：

Tool: SN-Query-Table
Parameters:
  table_name: cmdb_ci
  query: sys_idIN[comma_separated_parent_ids]
  fields: sys_id,name,sys_class_name,business_criticality,operational_status

多层依赖链（递归）：

Tool: SN-Execute-Background-Script
Parameters:
  description: Trace full upstream impact
  script: |
    var targetCiId = 'YOUR_CI_SYS_ID';
    var maxDepth = 5;
    var impactedCIs = [];
    var visited = {};

    function traceUpstream(ciId, depth) {
      if (depth > maxDepth || visited[ciId]) return;
      visited[ciId] = true;

      var gr = new GlideRecord('cmdb_rel_ci');
      gr.addQuery('child', ciId);
      gr.addQuery('type.parent_descriptor', 'CONTAINS', 'Depends');
      gr.query();

      while (gr.next()) {
        var parentId = gr.parent.toString();
        var parentCi = new GlideRecord('cmdb_ci');
        if (parentCi.get(parentId)) {
          impactedCIs.push({
            depth: depth,
            sys_id: parentId,
            name: parentCi.name.toString(),
            class: parentCi.sys_class_name.toString(),
            criticality: parentCi.business_criticality.toString()
          });
          traceUpstream(parentId, depth + 1);
        }
      }
    }

    traceUpstream(targetCiId, 1);

    gs.info('=== UPSTREAM IMPACT ANALYSIS ===');
    gs.info('Total CIs impacted: ' + impactedCIs.length);
    impactedCIs.forEach(function(ci) {
      gs.info('Level ' + ci.depth + ': ' + ci.name + ' (' + ci.class + ') - Criticality: ' + ci.criticality);
    });

步骤 3：识别受影响的业务服务

业务服务位于依赖链的顶层，代表业务价值：

查找直接关联的服务：

Tool: SN-Query-Table
Parameters:
  table_name: service_ci_assoc
  query: ci_id=[ci_sys_id]
  fields: service_id,service_id.name,service_id.operational_status

通过关系链查找服务：

Tool: SN-Query-Table
Parameters:
  table_name: cmdb_rel_ci
  query: child=[ci_sys_id]^parent.sys_class_nameLIKEcmdb_ci_service
  fields: parent,parent.name,parent.operational_status,parent.busines_criticality

全面分析服务影响：

Tool: SN-Execute-Background-Script
Parameters:
  description: Find all affected business services
  script: |
    var targetCiId = 'YOUR_CI_SYS_ID';
    var affectedServices = [];
    var visited = {};

    function findServices(ciId, path) {
      if (visited[ciId]) return;
      visited[ciId] = true;

      // Check if this CI is a service
      var ci = new GlideRecord('cmdb_ci');
      if (ci.get(ciId)) {
        if (ci.sys_class_name.toString().indexOf('cmdb_ci_service') !== -1) {
          affectedServices.push({
            sys_id: ciId,
            name: ci.name.toString(),
            criticality: ci.business_criticality.toString(),
            path: path.join(' -> ')
          });
          return;
        }
      }

      // Check direct service associations
      var assoc = new GlideRecord('service_ci_assoc');
      assoc.addQuery('ci_id', ciId);
      assoc.query();
      while (assoc.next()) {
        var svc = new GlideRecord('cmdb_ci_service');
        if (svc.get(assoc.service_id)) {
          affectedServices.push({
            sys_id: svc.sys_id.toString(),
            name: svc.name.toString(),
            criticality: svc.business_criticality.toString(),
            path: path.join(' -> ') + ' -> (direct association)'
          });
        }
      }

      // Traverse upstream
      var gr = new GlideRecord('cmdb_rel_ci');
      gr.addQuery('child', ciId);
      gr.query();
      while (gr.next()) {
        var parentId = gr.parent.toString();
        var parentCi = new GlideRecord('cmdb_ci');
        if (parentCi.get(parentId)) {
          findServices(parentId, path.concat([parentCi.name.toString()]));
        }
      }
    }

    var startCi = new GlideRecord('cmdb_ci');
    startCi.get(targetCiId);
    findServices(targetCiId, [startCi.name.toString()]);

    gs.info('=== AFFECTED BUSINESS SERVICES ===');
    gs.info('Total services: ' + affectedServices.length);
    affectedServices.forEach(function(svc) {
      gs.info('Service: ' + svc.name + ' | Criticality: ' + svc.criticality);
      gs.info('  Path: ' + svc.path);
    });

步骤 4：评估业务关键性

CI 关键性决定变更风险级别：

业务关键性值：

值	标签	描述	变更风险
1	最关键	核心业务运营	很高
2	关键	重要业务功能	高
3	重要	支持性功能	中
4	较重要	非必要功能	低
5	非关键	对业务影响极小	很低

计算综合风险：

Tool: SN-Execute-Background-Script
Parameters:
  description: Calculate change risk score
  script: |
    var targetCiId = 'YOUR_CI_SYS_ID';
    var impactData = {
      directCriticality: '',
      servicesImpacted: 0,
      criticalServicesImpacted: 0,
      totalDependentCIs: 0,
      riskScore: 0
    };

    // Get target CI criticality
    var targetCi = new GlideRecord('cmdb_ci');
    if (targetCi.get(targetCiId)) {
      impactData.directCriticality = targetCi.business_criticality.toString() || '5';
    }

    // Count dependent CIs and criticality
    var visited = {};
    function countImpact(ciId) {
      if (visited[ciId]) return;
      visited[ciId] = true;

      var gr = new GlideRecord('cmdb_rel_ci');
      gr.addQuery('child', ciId);
      gr.query();

      while (gr.next()) {
        var parentCi = new GlideRecord('cmdb_ci');
        if (parentCi.get(gr.parent)) {
          impactData.totalDependentCIs++;

          if (parentCi.sys_class_name.toString().indexOf('service') !== -1) {
            impactData.servicesImpacted++;
            if (parseInt(parentCi.business_criticality) <= 2) {
              impactData.criticalServicesImpacted++;
            }
          }

          countImpact(gr.parent.toString());
        }
      }
    }

    countImpact(targetCiId);

    // Calculate risk score (1-10)
    var critScore = 6 - parseInt(impactData.directCriticality || 5);
    var svcScore = Math.min(impactData.servicesImpacted * 2, 4);
    var critSvcScore = impactData.criticalServicesImpacted * 2;
    impactData.riskScore = Math.min(critScore + svcScore + critSvcScore, 10);

    gs.info('=== RISK ASSESSMENT ===');
    gs.info('Direct CI Criticality: ' + impactData.directCriticality);
    gs.info('Dependent CIs: ' + impactData.totalDependentCIs);
    gs.info('Services Impacted: ' + impactData.servicesImpacted);
    gs.info('Critical Services: ' + impactData.criticalServicesImpacted);
    gs.info('RISK SCORE: ' + impactData.riskScore + '/10');
    gs.info('Recommendation: ' + (impactData.riskScore >= 7 ? 'CAB REVIEW REQUIRED' : impactData.riskScore >= 4 ? 'Peer Review Recommended' : 'Standard Change Process'));

步骤 5：生成影响报告

创建供 CAB 审核的全面影响报告：

以结构化格式获取所有影响数据：

Tool: SN-Execute-Background-Script
Parameters:
  description: Generate comprehensive impact report
  script: |
    var targetCiId = 'YOUR_CI_SYS_ID';
    var report = {
      generatedAt: new GlideDateTime().getDisplayValue(),
      targetCI: {},
      upstreamImpact: [],
      downstreamImpact: [],
      affectedServices: [],
      affectedUsers: 0,
      riskLevel: '',
      recommendations: []
    };

    // Target CI details
    var targetCi = new GlideRecord('cmdb_ci');
    if (targetCi.get(targetCiId)) {
      report.targetCI = {
        name: targetCi.name.toString(),
        class: targetCi.sys_class_name.toString(),
        criticality: targetCi.business_criticality.getDisplayValue(),
        environment: targetCi.environment.toString(),
        supportGroup: targetCi.support_group.getDisplayValue(),
        location: targetCi.location.getDisplayValue()
      };
    }

    // Upstream (what depends on this)
    var upGr = new GlideRecord('cmdb_rel_ci');
    upGr.addQuery('child', targetCiId);
    upGr.query();
    while (upGr.next()) {
      var upCi = new GlideRecord('cmdb_ci');
      if (upCi.get(upGr.parent)) {
        report.upstreamImpact.push({
          name: upCi.name.toString(),
          class: upCi.sys_class_name.toString(),
          criticality: upCi.business_criticality.getDisplayValue()
        });
      }
    }

    // Downstream (what this depends on)
    var downGr = new GlideRecord('cmdb_rel_ci');
    downGr.addQuery('parent', targetCiId);
    downGr.query();
    while (downGr.next()) {
      var downCi = new GlideRecord('cmdb_ci');
      if (downCi.get(downGr.child)) {
        report.downstreamImpact.push({
          name: downCi.name.toString(),
          class: downCi.sys_class_name.toString()
        });
      }
    }

    // Services
    var svcAssoc = new GlideRecord('service_ci_assoc');
    svcAssoc.addQuery('ci_id', targetCiId);
    svcAssoc.query();
    while (svcAssoc.next()) {
      var svc = new GlideRecord('cmdb_ci_service');
      if (svc.get(svcAssoc.service_id)) {
        report.affectedServices.push({
          name: svc.name.toString(),
          criticality: svc.business_criticality.getDisplayValue()
        });
      }
    }

    // Estimate affected users (if service has user_base field)
    report.affectedServices.forEach(function(svc) {
      var svcGr = new GlideRecord('cmdb_ci_service');
      svcGr.addQuery('name', svc.name);
      svcGr.query();
      if (svcGr.next() && svcGr.user_base) {
        report.affectedUsers += parseInt(svcGr.user_base) || 0;
      }
    });

    // Risk level
    var criticalCount = report.affectedServices.filter(function(s) {
      return s.criticality === 'Most Critical' || s.criticality === 'Critical';
    }).length;

    if (criticalCount > 0 || report.upstreamImpact.length > 10) {
      report.riskLevel = 'HIGH';
      report.recommendations.push('Schedule during maintenance window');
      report.recommendations.push('Prepare rollback plan');
      report.recommendations.push('Notify affected service owners');
    } else if (report.upstreamImpact.length > 3) {
      report.riskLevel = 'MEDIUM';
      report.recommendations.push('Peer review recommended');
      report.recommendations.push('Test in non-prod first');
    } else {
      report.riskLevel = 'LOW';
      report.recommendations.push('Standard change process');
    }

    gs.info(JSON.stringify(report, null, 2));

步骤 6：将影响关联到变更请求

将影响分析与变更请求关联起来：

将受影响的 CI 添加到变更中：

Tool: SN-Create-Record
Parameters:
  table_name: task_ci
  data:
    task: [change_request_sys_id]
    ci_item: [affected_ci_sys_id]

使用影响摘要更新变更：

Tool: SN-Update-Record
Parameters:
  table_name: change_request
  sys_id: [change_sys_id]
  data:
    impact: 2  # 1=High, 2=Medium, 3=Low
    risk: "Medium"
    business_duration: "4 hours"
    justification: "Impact analysis shows 5 dependent services, 2 critical"

工具用法摘要

操作	MCP 工具	REST 端点
查找 CI	SN-Query-Table、SN-List-CmdbCis	GET /cmdb_ci
查询关系	SN-Query-Table	GET /cmdb_rel_ci
查找服务	SN-Query-Table	GET /cmdb_ci_service
服务关联	SN-Query-Table	GET /service_ci_assoc
复杂分析	SN-Execute-Background-Script	POST /api/sn_chg_rest
关联到变更	SN-Create-Record	POST /task_ci

最佳实践

• **先广后深：**先识别所有第一层依赖，再递归追踪
• **考虑两个方向：**影响会沿上游（依赖项）传播，也会沿下游（基础设施）传播
• **考虑时间因素：**同一项变更在工作时间和维护窗口期间造成的影响不同
• **记录假设：**记录 CMDB 中未体现的关系假设
• **提交 CAB 前进行验证：**提交给 CAB 前，手动验证关键路径
• **先更新 CMDB：**如果缺少关系，请在完成影响分析前添加这些关系

风险评估矩阵

标准	低（1 分）	中（2 分）	高（3 分）
CI 关键性	非关键	重要	关键／最关键
受影响的服务	0-1	2-5	6+
关键服务	0	1	2+
用户影响	<100	100-1000	1000+
恢复时间	<1 小时	1-4 小时	4+ 小时

风险评分说明：

• 5-7：低风险 - 标准变更流程
• 8-11：中风险 - 需要同行评审
• 12-15：高风险 - 需要 CAB 评审

故障排查

影响分析未显示任何依赖关系

症状： CI 显示没有上游影响，但显然被服务使用 原因： CMDB 中缺少关系 解决方案： 使用 cmdb/relationship-mapping 技能检查并创建缺失的关系

受影响项中未显示服务

症状： 已知的业务服务未显示为受影响 原因： 缺少 service_ci_assoc 记录或关系 解决方案：

1. 检查 service_ci_assoc 中是否存在直接关联
2. 检查 cmdb_rel_ci 中的关系链
3. 创建缺失的关联

风险评分似乎过低

症状： 关键基础设施的风险评分较低 原因： CI 未设置业务关键性 解决方案： 分析前更新 CI 上的 business_criticality 字段

递归查询超时

症状： 复杂环境中的后台脚本超时 原因： 递归层级过多或查询优化不佳 解决方案： 降低 maxDepth，或使用带限制的索引查询

示例

示例 1：数据库服务器维护影响

# 1. Find the database server
Tool: SN-Query-Table
Parameters:
  table_name: cmdb_ci_server
  query: name=prod-db-01
  fields: sys_id,name,business_criticality

# Result: sys_id = abc123, criticality = 2 (Critical)

# 2. Find what runs on this server
Tool: SN-Query-Table
Parameters:
  table_name: cmdb_rel_ci
  query: child=abc123^type.parent_descriptorLIKERuns
  fields: parent.name,parent.sys_class_name

# Result: Oracle DB Instance, MySQL Instance

# 3. Find what depends on these databases
Tool: SN-Query-Table
Parameters:
  table_name: cmdb_rel_ci
  query: child.nameLIKEOracle^ORchild.nameLIKEMySQL
  fields: parent.name,parent.sys_class_name

# Result: ERP Application, HR Portal, Customer Portal

# 4. Find affected services
Tool: SN-Query-Table
Parameters:
  table_name: service_ci_assoc
  query: ci_id.nameLIKEPortal^ORci_id.nameLIKEERP
  fields: service_id.name,service_id.business_criticality

# Result:
#   - Customer Service (Critical)
#   - HR Services (Important)
#   - Finance Operations (Most Critical)

# CONCLUSION: HIGH RISK - 3 services affected, 2 critical

示例 2：应用部署影响

# Scenario: Deploying new version of "Portal Frontend" application

# 1. Get application CI
Tool: SN-List-CmdbCis
Parameters:
  ci_class: cmdb_ci_appl
  query: name=Portal Frontend
  fields: sys_id,business_criticality,support_group

# 2. Run full impact analysis script (from Step 5)
# This returns structured JSON with:
# - All dependent CIs
# - Affected services
# - Risk score
# - Recommendations

# 3. Create impact record for change
Tool: SN-Update-Record
Parameters:
  table_name: change_request
  sys_id: CHG0012345_sys_id
  data:
    impact: 2
    risk: "Medium"
    justification: |
      Impact Analysis Results:
      - 1 Business Service Affected: Customer Portal
      - 3 Dependent Components: Load Balancer, CDN, Auth Service
      - Risk Score: 6/10
      - Recommended: Peer review, rollback plan ready

相关技能

• cmdb/relationship-mapping - 创建和验证关系
• cmdb/ci-discovery - CI 创建与分类
• cmdb/data-quality - 确保 CMDB 准确性，以便可靠地进行影响分析
• itsm/change-management - 变更请求工作流

参考资料

• ServiceNow 影响分析
• CMDB 健康状况仪表板
• ITIL 变更管理
• ServiceNow 变更风险评估