Objective

In this Case File, you'll run the same import three times while changing only one setting: the Transform Map's coalesce configuration.

By comparing the results of each import, you'll see how ServiceNow decides whether an incoming row updates an existing CI or inserts a new one.

This exercise demonstrates one of the most common causes of duplicate records in a CMDB.

Difficulty

Intermediate

Estimated Time: 20–30 minutes

Skills Practiced

• Import Sets
• Transform Maps
• Coalesce
• CMDB
• Record Matching
• Data Integrity

Lab Overview

You'll use the same spreadsheet for all three experiments.

The import data never changes.

Only the Transform Map's coalesce configuration changes.

After each import, compare the resulting CIs and determine why ServiceNow made that decision.

Starting Database

Verify these Linux Server records exist before beginning.

Import Data

Create an Import Set using the following rows.

Load the data, but don't run the Transform yet.

Before You Begin

Take a moment to predict the outcome before each experiment.

You'll learn more by committing to an answer before seeing the results.

Experiment 1 — No Coalesce

Open the Transform Map and verify that no field is marked as Coalesce.

Run the Transform.

Expected Results

You should now have six Linux Server records.

Observation

Without a coalesce field, ServiceNow has no way to associate incoming rows with existing records.

Every row is treated as a new insert.

Reset

Delete the imported records and return the table to its original three-record state.

Prediction

Configure Name as the only coalesce field.

Before running the import, decide which rows you expect to update and which you expect to insert.

Experiment 2 — Coalesce on Name

Enable Coalesce on the Name field only.

Run the Transform.

Expected Results

Observation

The renamed server shares the same IP Address and Serial Number as an existing CI, but ServiceNow ignores those values because Name is the only field participating in record matching.

No name match means no update.

Why It Works This Way

Coalesce is an exact matching rule.

If the configured field (or fields) matches an existing record, ServiceNow performs an update.

If no match is found, ServiceNow inserts a new record.

The platform doesn't compare other fields or attempt to determine whether two records "look similar."

Reset Again

Delete the imported records and restore the original three CIs.

Prediction

This time configure IP Address and Serial Number as coalesce fields.

What do you expect to happen to the renamed server?

Experiment 3 — Multi-Field Coalesce

Enable Coalesce on:

• IP Address
• Serial Number

Run the Transform.

Expected Results

Notice that LNX-DB-02 is now LNX-DB-02-RENAMED.

Although the hostname changed, ServiceNow identified the existing CI using the combination of IP Address and Serial Number before applying the update.

Challenge

Without running another import, answer this question first.

What happens if Serial Number is the only coalesce field?

Would all three rows still behave as expected?

Would any duplicates be created?

Make your prediction, then test it by modifying the Transform Map.

Key Takeaways

• Coalesce defines a record's identity during an import.
• ServiceNow only evaluates the fields marked as Coalesce.
• Matching is exact—there is no similarity check or "best guess."
• Choosing unstable identifiers (such as hostnames) increases the risk of duplicate CIs.
• Stable identifiers, such as Serial Number or a combination of immutable fields, produce more reliable imports.

Why This Matters

This lab uses three records so the behavior is easy to observe.

Now imagine the same Transform Map importing 50,000 CIs into a production CMDB.

A poor coalesce strategy can create thousands of duplicate records in a single import, affecting discovery, reporting, asset relationships, and every process that relies on CMDB data.

Understanding how ServiceNow matches records is more than an exam topic—it's a fundamental skill for building and maintaining a healthy CMDB.