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Brent G Saucedo
Brent G Saucedo

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The Ultimate ServiceNow CIS-DF (Data Foundations) Exam Cheat Sheet

#servicenow #certification #cmdb #devops

The Certified Implementation Specialist - Data Foundations (CIS-DF) is one of the most critical exams in the ServiceNow ecosystem right now. It is no longer just about "how to create a CI class." It is about Governance, CSDM, IRE logic, and Health.

If you are an Architect, Implementer, or CMDB Admin preparing for this exam, this deep-dive cheat sheet covers the granular details you need to pass.

1. Common Service Data Model (CSDM)

The framework connecting business strategy to technical implementation.

The 5 Domains (Memorize the Tables & Colors)

Domain Color Key Tables 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

  • Business Application (cmdb_ci_business_app): The inventory record (e.g., "Zoom"). Non-operational. You cannot open an incident against this.
  • Application Service (cmdb_ci_service_auto): The deployed instance (e.g., "Zoom - Production"). Operational. Incidents live here.
  • Dynamic CI Group (cmdb_ci_query_based_service): A wrapper CI that groups CIs based on a query (e.g., "All Linux Servers in NY").

CSDM 4.0 Lifecycle Standards

Stop using install_status or operational_status. The new standard uses two fields on cmdb_ci:

  1. lifecycle_stage (e.g., Operational, End of Life)
  2. lifecycle_stage_status (e.g., In Use, Retired, Obsolete)

Exam Tip: You must use the CSDM Lifecycle Mapping tool to map legacy status fields to these new standard fields. The system then keeps them in sync automatically.

⚙️ 2. Identification & Reconciliation Engine (IRE)

The "Gatekeeper" that prevents duplicates and manages data source priority.

The IRE Processing Order (Crucial!)

You must know the exact order in which the IRE processes a payload:

  1. Input Payload: JSON arrives (Discovery, Import Set, etc.).
  2. Identification Rules: "Does this CI exist?"
    • Checks Class priority (e.g., Serial Number -> Name + Mac Address).
    • Match = Update / No Match = Create.
  3. Reconciliation Rules: "Is this source allowed to update this attribute?"
    • Checks Data Source Precedence.
    • Example: ServiceGraph-SCCM (Priority 100) vs. Manual (Priority 500). Lower number wins.
  4. 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.
  5. Multi-Source CMDB: Updates sys_object_source history.

Key IRE Concepts

  • sys_object_source Table: The "Rosetta Stone." Maps a Native Key (e.g., SCCM Resource ID) to a ServiceNow Sys ID.
  • Independent CIs: Can exist alone (Server, Switch).
  • Dependent CIs: Cannot exist without a parent (Network Card, Hard Drive). Identified by Parent ID + Local Attribute.
  • De-Duplication: If IRE finds two matches for one payload, it halts. It creates a De-duplication Task and does not update the records.

3. CMDB Health Dashboard

The "Vital Signs" calculated via scheduled jobs.

The 3 "C"s Metric Categories

1. Completeness (Are fields filled?)

  • Required: Mandatory in System Dictionary (Global).
  • Recommended: Marked in CI Class Manager (Soft check).

2. Correctness (Is data accurate?)

  • Duplicate: Based on Identification Rules.
  • Orphan:
    • Logical: Item missing required data (e.g., Virtual Machine missing a "Virtual" flag).
    • Relationship: Dependent CI (NIC) lost its Parent (Server).
  • Staleness: CI not updated in X days (Default: 60).

3. Compliance (Does it follow rules?)

  • Uses Audits and Desired State to check logical conditions (e.g., "All Prod Servers must have 16GB RAM").

4. CMDB Data Manager

The modern way to handle Lifecycle (Retire/Archive/Delete).

This replaces the legacy "Data Certification" plugin for lifecycle management. It is policy-driven.

  1. Policy: Filter criteria (e.g., "Servers not discovered in 6 months").
  2. Action:
    • Retire: Set status to Retired.
    • Archive: Move from cmdb_ci to ar_cmdb_ci (Flattened, read-only storage).
    • Delete: Permanently destroy.
  3. Attestation: Send a task to the CI Owner to verify the CI before taking action.

5. Advanced Concepts & Gotchas

CMDB 360 (Multisource CMDB)

  • Problem: Discovery says RAM is 8GB. SCCM says 16GB. Who is right?
  • Solution: CMDB 360 stores every value submitted by every source in the cmdb_multisource_data table.
  • Use Case: You can revert a specific field to a previous value from a specific source without re-running discovery.

Principal Class Filter

  • Concept: There are too many CIs in the cmdb_ci table (Printers, Routers, Mice).
  • Feature: The "Principal Class" filter limits what users see in reference fields (like on the Incident form) to only the "Big" CIs (Servers, Apps, Databases).

Service 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; answer 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 with your CIS-DF!

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