CMDB schema model

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  • Updated March 12, 2026
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    Summary of CMDB schema model

    The CMDB schema model in ServiceNow is a connected structure of tables that store information about all assets, business services, and their configurations managed by an organization. It supports IT and non-IT configuration items (CIs) and their relationships, enabling a comprehensive view of the network environment and dependencies.

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    This model is foundational for IT operations, as it integrates with applications like Asset Management and Contract Management, linking hardware, software, contracts, licenses, and vendor information to provide a unified configuration management database.

    Key Features

    • Core Tables and Classes: The Base Configuration Item [cmdb] table manages non-IT CIs, while the Configuration Item [cmdbci] table and its extended classes handle IT CIs such as servers, databases, computers, and network devices.
    • Class Hierarchy and Extensions: Classes extend from general to specific types (e.g., Computer to Server to UNIX Server), allowing detailed classification and attribute management.
    • CI Relationships: The CI Relationship [cmdbrelci] class defines dependencies and relationships between CIs, critical for impact analysis and operational awareness.
    • Schema Map Tool: Accessible via System Definition > Tables & Columns, the schema map visualizes table structures and their relationships for better schema understanding.
    • Attribute Management: Attributes define CI characteristics and classification hierarchy. Modifying or adding unique attributes involves extending class tables and creating new classifications, reflecting the diverse nature of IT and non-IT assets.
    • Related ServiceNow Store Apps: Apps such as CMDB CI Class Models, Discovery Patterns, and Service Graph Connectors enhance CMDB capabilities by adding class models, discovery logic, and third-party integrations.

    Key Outcomes

    • Enables accurate tracking and management of all configuration items and their relationships within an enterprise environment.
    • Supports IT service management processes by providing a reliable source of configuration data that integrates with asset and contract management functions.
    • Facilitates prioritization of key infrastructure classes (e.g., servers, databases, network devices) as Principal Classes to monitor health and business impact effectively.
    • Improves operational insight by visualizing CI dependencies and classification hierarchies, aiding in incident triage, change management, and impact analysis.

    The CMDB schema model is a series of connected tables that contain all the assets and business services controlled by a company and its configurations.

    Related ServiceNow® Store apps and reference information:
    • CMDB tables descriptions: Descriptions of key CMDB tables in the base system.
    • CMDB CI Class Models: A ServiceNow Store app that adds class models that extend the base CMDB class hierarchy. This includes class descriptions, identification rules, identifier entries, and dependent relationships if applicable. You can then use the added classes as any other CMDB base class.
    • Populating the CMDB: Information about the various options for populating the CMDB.
    • Discovery patterns: A ServiceNow Store app that provides a library of Discovery patterns for discovering specific devices and applications in the industry.
    • Getting started with Service Graph Connectors: ServiceNow Store apps that provide pre-defined integrations for importing and integrating common third-party data into CMDB classes. Also includes the IntegrationHub ETL wizard for creating new ETL transform maps.

    CMDB tables contain information about computers and devices on the network, software contracts and licenses, business services, and so on. The IT desk can use the CMDB to better understand their network users' equipment, and the relationships between them. The CMDB can also be referenced by other processes within the system.

    Applications such as Asset Management and Contract Management, operate in conjunction with the CMDB. Asset Management and Software Asset Management link to CMDB all assets, hardware, software, assets in stock, as well as records for manufacturers and vendors. The Contract Management application contains information about contracts, including leases, service contracts, purchase orders, warranties, and software licenses. The Configuration Management Database (CMDB) application has a focus on operation.

    For more background information about the CMDB, see the ServiceNow Community post at CMDB 101- What is a configuration management database and why do you need one?.

    Key class categories

    The following items are class categories that are typically key in organizations. You can for example, use this list as a general guideline for designating classes as Principal Class so you can track health and pay attention to the most important classes in your CMDB:
    • Servers (physical and virtual): Classes that are typically well-understood, relatively stable, and which form the backbone of most infrastructure.
    • Databases: Classes of high business impact, critical for incident triage, and relatively straightforward to discover and maintain.
    • Network devices (core infrastructure): Classes such as routers, switches, firewalls, and load balancers—hardware that connects everything. If setting as Principal Class, then as a general guideline, prioritize core and critical devices over access switches.
    • Application servers.
    • Storage.
    For more information, see Principal Class.

    Key CMDB classes

    Key classes in the CMDB:

    • The Base Configuration Item [cmdb] class, which is the core CMDB table for non IT CIs (descending classes are non IT CIs).
    • The core Configuration Item [cmdb_ci] class, which stores the basic attributes of all the CIs. The sn_cmdb_admin, sn_cmdb_editor, asset, admin, or itil user role is required to access this table (descending classes are IT CIs).
    • The CI Relationship [cmdb_rel_ci] class, which defines all relationships between CIs.

    The Configuration Item class is extended to other classes, such as Database [cmdb_ci_database] and Computer [cmdb_ci_computer]. The Computer class is extended to the Server [cmdb_ci_server] class, which is extended to the UNIX Server [cmdb_ci_unix_server] class, and so on.

    Note:
    The Base Configuration Item [cmdb] class uses the table per partition extension model, which has different behaviors for replicating and deriving information than other extended tables. See Table extension and classes.
    You can use the schema map to view more details of tables and their relationships:
    1. Navigate to System Definition > Tables & Columns.
    2. Select a table and then select Schema Map.
    Note:
    CIs not extended from the Configuration Item [cmdb_ci] table, are not displayed in Dependency Views maps and in CI relation formatters.

    CI attributes

    Attributes apply to all the CIs in a classification. To change attribute values for a CI, edit the appropriate CI. To add a unique attribute to a class, extend the class table and create a new classification for that CI.

    The position of a CI in a classification hierarchy is determined by the attributes it shares with the CIs below it. Each time a CI has a single different attribute from its parent, the classification hierarchy branches.

    For example, servers have different attributes from computers, which include workstations and laptops. Linux servers and UNIX servers have different attributes from the parent server classification and from each other, so they occupy separate branches in the hierarchy.