CMDB &
Config Management
ServiceNow's single source of truth for all IT infrastructure. CI classes, cmdb_ci hierarchy, CI relationships (cmdb_rel_ci), Discovery & IRE (deduplication/reconciliation), and CMDB Health scoring (Completeness + Compliance + Correctness).
Key traps: relationship direction ("Depends on::Used by" — know which side is parent/child), IRE vs legacy cmdb_dedupe (IRE is modern, fires on all CI inserts), and the 3 C's of CMDB Health (Completeness, Compliance, Correctness). CMDB is measured per class — a single class with bad data drags overall scores.
Part 5 Study Modules
CMDB Architecture & CI Classes
cmdb_ci base class, CI class hierarchy (hardware → computer → Windows Server), sys_class_name discriminator, Class Manager tool, and single-table inheritance for all CIs.
CI Relationships & Dependency
cmdb_rel_ci table, cmdb_rel_type bidirectional labels (Parent::Child format), dependency maps, service maps, and how affected CIs are calculated on incidents.
Discovery & IRE
Discovery MID Server probes/sensors, Identification & Reconciliation Engine (identification rules, reconciliation rules), IRE vs legacy dedupe, and data source priority resolution.
CMDB Health & Governance
CMDB Health Dashboard, 3 C's (Completeness/Compliance/Correctness), per-class scoring, staleness, CMDB Remediation Tasks, and CSDM as architectural best practice.
CI Class Manager & Dynamic CI Groups
CI Class Manager as the correct tool for extending the CMDB hierarchy (not direct schema edits), u_ prefix for custom fields, extending vs. modifying baseline classes, Dynamic CI Groups (condition-based auto-updating membership), and CI Group-based Discovery for ongoing CI refresh.
CSDM Framework — The Four Domains
Common Service Data Model four domains: Business (capabilities/applications), Design (services/offerings), Manage (technical services/vendors), Infrastructure CIs. Business Application (cmdb_ci_business_app) vs. Application Service (cmdb_ci_service_auto) distinction. CSDM 5 Service Instance rename. CSDM adoption journey.
CSDM Service Modeling — Building the Service Map
Linking Business Applications to Application Services (Service Mapping vs. manual), impact propagation chain (CI → Application Service → Business Application), Change Impact Analysis flow, business_criticality field, ownership field distinctions, and CSDM modeling mistakes.
CSDM CI Alignment — Using the Right CI Classes
Why CI class mismatches break CSDM, prescribed CI classes by CSDM domain, service_type field on cmdb_ci_service (critical — distinguishes 3 service types on same table), Discovery Pattern class assignment, SGC cloud class mapping, CSDM Alignment Report, CI Lifecycle events and CSDM actions.