The Ultimate ServiceNow CIS-DF (Data Foundations) Exam Cheat Sheet
Source: Dev.to
Common Service Data Model (CSDM)
The framework that connects business strategy to technical implementation.
The 5 Domains (Memorize the Tables & Colors)
| Domain | Color | Key Tables (examples) | Purpose | Persona |
|---|---|---|---|---|
| Foundation | ⚪ Grey | sys_user, cmn_location, core_company | Referential data used by all domains. Mostly non‑CMDB. | Data Steward |
| Design | 🟠 Orange | cmdb_ci_business_app, cmdb_ci_business_capability | Strategy – what the business wants/needs (pre‑build). | Enterprise Architect |
| Build | 🔴 Red | cmdb_ci_sdlc_component, cmdb_ci_service | DevOps – the logical code and artifacts. | App Developer |
| Manage Tech | 🟢 Green | cmdb_ci_service_technical, cmdb_ci_query_based_service | Ops – the deployed “engine room” (infrastructure). | Tech Service Owner |
| Sell/Consume | 🔵 Blue | cmdb_ci_service_business, service_offering | Portfolio – what the business consumes (the menu). | Portfolio Manager |
Critical Table Distinctions
| CI Type | Table | Description | Operational? |
|---|---|---|---|
| Business Application | cmdb_ci_business_app | Inventory record (e.g., “Zoom”). Non‑operational. | No |
| Application Service | cmdb_ci_service_auto | Deployed instance (e.g., “Zoom – Production”). Operational. | Yes |
| Dynamic CI Group | cmdb_ci_query_based_service | Wrapper CI that groups CIs based on a query (e.g., “All Linux Servers in NY”). | N/A |
CSDM 4.0 Lifecycle Standards
install_status and operational_status are deprecated. The new standard uses two fields on cmdb_ci:
lifecycle_stage– e.g., Operational, End of Lifelifecycle_stage_status– e.g., In Use, Retired, Obsolete
Exam tip: Use the CSDM Lifecycle Mapping tool to map legacy status fields to these new fields; the system then keeps them in sync automatically.
Identification & Reconciliation Engine (IRE)
The “Gatekeeper” that prevents duplicates and manages data‑source priority.
IRE Processing Order (Crucial!)
- Input Payload – JSON arrives (Discovery, Import Set, etc.).
- Identification Rules – “Does this CI exist?”
- Checks class priority (e.g., Serial Number → Name + MAC Address).
- Match → Update No Match → Create.
- Reconciliation Rules – “Is this source allowed to update this attribute?”
- Checks Data Source Precedence (lower number = higher priority).
- Example: ServiceGraph‑SCCM (Priority 100) vs. Manual (Priority 500).
- IRE Data Refresh Rules – “Is the high‑priority data stale?”
- Allows a lower‑priority source to update a locked field if the primary source hasn’t reported in X days.
- Updates
sys_object_sourcehistory in a Multi‑Source CMDB.
Key IRE Concepts
sys_object_sourcetable – The “Rosetta Stone.” Maps a native key (e.g., SCCM Resource ID) to a ServiceNowsys_id.- Independent CIs – Can exist alone (Server, Switch).
- Dependent CIs – Require a parent (Network Card, Hard Drive). Identified by
Parent ID+Local Attribute. - De‑duplication – If IRE finds two matches for a single payload, it halts, creates a De‑duplication Task, and does not update any records.
CMDB Health Dashboard
The “Vital Signs” calculated via scheduled jobs.
The 3 “C” Metric Categories
| Category | What It Measures | How It’s Determined |
|---|---|---|
| Completeness | Are required fields filled? | Required – mandatory in System Dictionary (global). Recommended – flagged in CI Class Manager (soft check). |
| Correctness | Is the data accurate? | Duplicate – based on Identification Rules. Orphan – • Logical: missing required data (e.g., VM without “Virtual” flag). • Relationship: dependent CI lost its parent (NIC without Server). Staleness – CI not updated in X days (default = 60). |
| Compliance | Does the CI follow policy rules? | Uses Audits and Desired State to enforce logical conditions (e.g., “All Prod Servers must have ≥ 16 GB RAM”). |
CMDB Data Manager
The modern, policy‑driven way to handle lifecycle (Retire / Archive / Delete).
It replaces the legacy Data Certification plugin.
- Policy – Filter criteria (e.g., “Servers not discovered in 6 months”).
- Action –
- Retire – Set status to Retired.
- Archive – Move from
cmdb_citoar_cmdb_ci(flattened, read‑only storage). - Delete – Permanently destroy.
- Attestation – Sends a task to the CI Owner to verify the CI before any action is taken.
Advanced Concepts & Gotchas
CMDB 360 (Multi‑Source CMDB)
Problem: Discovery reports RAM = 8 GB, SCCM reports RAM = 16 GB. Which value wins?
Solution: cmdb_multisource_data stores every value submitted by every source. You can revert a specific field to a previous value from a chosen source without re‑running discovery.
Principal Class Filter
Concept: The cmdb_ci table can become cluttered (Printers, Routers, Mice, …).
Feature: The Principal Class filter limits what users see in reference fields (e.g., on the Incident form) to only the “big” CIs (Servers, Applications, Databases).
Service G
(Content truncated in the original source.)
Graph Connectors (SGC)
Rule: Always prefer SGC over custom Import Sets.
Why: They come with pre‑built IRE mappings and class structures certified by ServiceNow.
Exam Strategy Summary
-
Think like an Architect:
Don’t just answer how to configure it; explain why (governance, minimizing technical debt). -
IRE is King:
If you don’t understand how Identification and Reconciliation rules interact, you will struggle. -
CSDM is the Map:
Know which table belongs to which domain and which Persona manages it.
Good luck on your CIS‑DF exam! Use this cheat sheet as a quick reference while you study and during the exam. 🚀