Hi everyone,

I wanted to share some insights on how relationship levels work in ServiceNow CMDB, especially for those who may not be familiar with this setting and its impact on performance and visibility. The information and examples below are referenced from our production instance, specifically using the 360 Encompass application CI as a case study.

What Are Relationship Levels?

In ServiceNow CMDB, the "relationship level" setting controls how many layers of CI (Configuration Item) relationships are loaded and displayed when you view a CI. This is crucial for understanding dependencies, impact analysis, and troubleshooting, but it also has a direct effect on system performance.

Real-World Example: 360 Encompass Application

Here's how different relationship levels affect what you see for a real application in our environment:

Level 1: Foundational Infrastructure

• Focus: Immediate dependencies and hosting environments.
• Example: 360 Encompass running directly on its Microsoft IIS Server. This shows the server instance where the application is hosted.

Level 2: Detailed Component Connections

• Focus: Deeper connections, including network and configuration details.
• Example: The database server supporting 360 Encompass, VMware Distributed Virtual Port Groups, and IIS Virtual Directories.

Level 3: Intermediate Detail (with Some VMware Info)

• Focus: Broader infrastructure, including some VMware-specific details.
• Example: Network switches connecting the database server to storage, "Hosted on - VMware vCenter Datacenters."

Level 4: Extensive VMware Infrastructure (Potentially Incomplete)

• Focus: Comprehensive VMware infrastructure relationships.
• Example: Power supply for network switches, VMware Virtual Machine Instances, VMware vCenter Clusters, HPE BladeSystem Blades.
• Note: At this level, you may encounter errors like "Maximum relationship limit has been reached" or "Maximum number of queries has been reached." The data may be partial or incomplete.

Level 5: Expanded Relationships (Likely Incomplete)

• Focus: Even broader set of relationships, including resource pools.
• Example: Maintenance contract for the power supply, ESX Resource Pools, further HPE BladeSystem details.
• Critical: Level 5 is heavily constrained by system limits, making the data potentially unreliable and incomplete.

Why Does This Matter?

• Performance: Higher levels (4 and 5) can cause significant slowdowns and incomplete data, especially during large-scale discovery or impact analysis.
• Accuracy: Data at higher levels may be partial or misleading due to system constraints.
• User Experience: The default relationship level is controlled by the "ecmdb.levels" user preference. If not set personally, the system uses the "empty user" default, which can affect all users.

What We Learned

• Lower levels (1 or 2) provide much better performance and a more responsive UI.
• Higher levels may not add value if the data is incomplete or inaccurate.
• It's important to balance visibility with performance, especially for critical use cases like incident management and root cause analysis.

Final Thoughts

If you're experiencing slow performance or incomplete dependency maps in your CMDB, consider reviewing and adjusting your relationship level settings. For most environments, a lower level (such as 2 or 3) offers the best balance between visibility and performance.

Reference:

This information is based on our production instance and real application data (360 Encompass). If you have questions or want to share your own experiences, please comment below!

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Selva Arun

ServiceNow Rising Star, 2024

ServiceNow Developer, UMass Memorial Health