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CI Classes & Relationships

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In this lesson, you will learn:

  • How CI classes are organized
  • How to explore classes with CI Class Manager
  • How CI relationships work

1 CI classes: a family tree

A laptop and a Linux server are both CIs, but they need different fields. So the CMDB uses classes, built with table extension, just like Task and Incident (Lesson 29.2). 🌳

Part of the CI class hierarchy. Configuration Item, cmdb_ci, is at the top. Below it, Hardware, cmdb_ci_hardware. Below that, Computer, cmdb_ci_computer. Below Computer, Server, cmdb_ci_server. Below Server, Linux Server, cmdb_ci_linux_server, and Windows Server, cmdb_ci_win_server. Each level adds fields: Hardware adds serial number, Computer adds RAM and CPU, Server adds used for.
Figure 1. Each class inherits the fields above it and adds its own.

Key term: CI class

A type of CI, stored as its own table, like cmdb_ci_linux_server. Child classes inherit their parent’s fields.

Explore classes in Configuration > CI Class Manager. It shows the tree, each class’s attributes, and its identification rules.

2 Relationships

CIs rarely live alone. An app runs on a server. A server depends on a database. These links are relationships, stored in cmdb_rel_ci.

Relationship type Example
Depends on :: Used by SNWR Email depends on MAILDB
Runs on :: Runs Exchange runs on mail01
Hosted on :: Hosts A virtual machine is hosted on a physical server
Contains :: Contained by A rack contains servers

📝 Note: Each type has two names, one for each direction. “mail01 Runs Exchange” and “Exchange Runs on mail01″ are the same link.

3 Seeing relationships

  • On a CI form, the Related Items section lists its upstream and downstream CIs.
  • Open the dependency view (map icon) to see them as a diagram.
  • Impact is about direction: if mail01 fails, everything that depends on it may fail too.

💡 Good to know: Put new CIs in the most specific class. A Linux server belongs in Linux Server, not in the generic Server or Computer class.

⭐ Remember: Classes = CI types in a tree. Relationships = links between CIs, stored in cmdb_rel_ci.

4 Let’s try it: climb the tree

  1. Open Configuration > CI Class Manager. Find Linux Server in the tree.
  2. Click it. Look at Attributes. Which were added by Linux Server, and which were inherited?
  3. Open any server CI with relationships. Look at Related Items, then open the dependency view.

5 Quick recap

  • CI classes form a tree, starting at cmdb_ci
  • Child classes inherit fields and add their own
  • CI Class Manager shows the tree and attributes
  • Relationships link CIs, like Runs on or Depends on
  • Use the dependency view to see impact

6 Check yourself

Think of your answer first. Then tap to check.

1 Where can you browse the CI class tree? Show answer

Configuration > CI Class Manager.

2 Which table stores CI relationships? Show answer

cmdb_rel_ci.

3 An app runs on mail01. mail01 goes down. Is the app affected? Show answer

Yes, likely. The app depends on the server it runs on.

Nice work! You finished this lesson. 🎉

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