What is CMDB?
A CMDB stores records called configuration items (CIs). A CI is anything IT has to manage to deliver a service: a laptop, a server, a virtual machine, a switch, an installed application, a cloud subscription, even a business service such as payroll. Each CI record holds attributes (name, model, serial number, OS version, location, owner, status) and, more importantly, its relationships to other CIs.
The idea comes from ITIL, the widely used IT service management framework, where configuration management is the practice of keeping accurate information about what IT runs and how the pieces fit together.
How a CMDB works
- Discovery and import: network discovery scans, endpoint agents (often from an RMM or other management tool) and imports from asset systems populate CI records. Manual entry fills the gaps.
- Relationships: the payroll application runs on a database server VM, which runs on a specific host, which connects to a specific switch. These links let the CMDB answer the question "what depends on this?"
- Service desk integration: tickets, incidents and change requests are linked to the CIs they affect, so each CI builds a history of problems and changes.
- Kept current through change management: each approved change updates the affected CI records. A CMDB that nobody updates drifts out of date, and a wrong CMDB can be worse than none because people trust it.
Change management and troubleshooting
Before a change, the CMDB supports impact analysis. If you plan to reboot a file server, its relationships show which applications, users and departments will be affected, which feeds the scope and risk analysis of the change request. During an incident, the CI history answers a classic troubleshooting question: what changed recently? If print jobs started failing the day after a driver update was recorded against the print server CI, you have a strong first theory.
Asset inventory vs. CMDB
| Question | Asset inventory | CMDB |
|---|---|---|
| Main purpose | What do we own, who has it and what did it cost? | How is it configured and what depends on it? |
| Typical fields | Asset tag, purchase date, warranty, license, assigned user | Configuration attributes, versions, relationships, linked incidents and changes |
| Scope | Mostly physical and financial items | Anything that supports a service, including software and services |
The two overlap and are often linked. A laptop has an asset record for its lifecycle, from procurement to disposal, and a CI record for its configuration. Smaller organizations often keep both in one tool.
CMDB on the CompTIA A+ exam
CMDB is on the A+ acronym list and belongs with Core 2's operational procedures material: documentation, asset management and change management. Know these points:
- CMDB expands to configuration management database, and it stores CIs and their relationships.
- If a question asks how to find which systems a planned change will affect, think CMDB.
- If it asks about tracking asset tags, warranties and assigned users, think asset management or an inventory list. A CMDB may hold that data, but the inventory is the narrower answer.
- Records stay accurate only when updating the CMDB is part of every approved change.
- Don't confuse CMDB with
cmd, the Windows command prompt.