What is the CMDB?
The Configuration Management Database (CMDB) is a set of tables that stores records about IT assets — Configuration Items (CIs). Servers, laptops, applications, network devices, databases, cloud resources — if IT manages it, it belongs in the CMDB.
Why the CMDB matters
The CMDB enables: impact analysis (if this server goes down, which services are affected?), change management (what CIs are affected by this change?), incident enrichment (auto-populate CI details when an incident is raised). Without accurate CMDB data, these capabilities do not work.
How CIs get into the CMDB
Three methods:
- ServiceNow Discovery — automated scanning of the network. The most reliable method for infrastructure CIs.
- Service Graph Connectors / integrations — pulling CI data from AWS, Azure, VMware, and other management tools.
- Manual entry or import — for CIs that cannot be discovered automatically (applications, services, relationships).
CI classes and the CMDB hierarchy
CIs are stored in type-specific tables. cmdb_ci is the base class. Servers use cmdb_ci_server, applications use cmdb_ci_appl, and so on. ServiceNow uses table inheritance — all CI records exist in cmdb_ci and in their specific class table simultaneously.
Relationships
Relationships define how CIs depend on each other. "Application X Runs on Server Y." "Service A Depends on Database B." Relationships are stored in cmdb_rel_ci. Accurate relationships are what enable impact analysis.
Why CMDB data degrades
Hardware gets decommissioned without removing the CI. Discovery runs find the CI is gone and mark it stale, but nobody cleans up the relationships. Applications get renamed or restructured. Manual entries are not updated when reality changes. Without a regular data quality process, CMDB health decays.
CMDB Health dashboard
Navigate to CMDB > CMDB Health. This dashboard shows completeness, compliance, and correctness scores per CI class. Use it to identify which classes need the most attention.