IRE Question

[Lucky1]

Hello all,

I see some articles, some community questions regarding Identification and Reconciliation Rules.

Can someone explain me the below question?

 We will configure Identification rules and as well as Reconciliation rules.

I have read that, based on Identifier entries, the CI will be identified and if the CI is found, then it will update the record, if No match is found it will create a record.

Here, my question is, " it " means who?

My First Question)

Is it like Identification rule will create a record?

My Second Question)

If the record exists, Is it like Identification rules updates the record or Reconciliation rule will update the record?

My third Question)

I understood, Reconciliation rules will come into picture if there are more than one data sources and this Reconciliation rules will only update the records but not used to create a records. Is it right? If so, why?

My last question) 

If we don't configure IRE rules, then if we run the discovery, then how it will create/update records in CMDB?

Regards,

Lucky

[Harish Bainsla]

Hi @Lucky1 

1.Is it like Identification rule will create a record?

Yes Identification rule is used to create or update the CI in cmdb .if a new record (like a Configuration Item, or CI) already exists in the system. If the rule identifies a match based on specific criteria, it will update the existing record. If no match is found, a new record will be created.

2.If the record exists, Is it like Identification rules updates the record or Reconciliation rule will update the record?

if a record exists, the reconciliation rule is responsible for updating the record with new information, not the identification rule. Because in reconciliation rule you will define which data source need to update which attribute in ci .

3.

I understood, Reconciliation rules will come into picture if there are more than one data sources and this Reconciliation rules will only update the records but not used to create a records. Is it right? If so, why?

Yes you are right 

4.

If we don't configure IRE rules, then if we run the discovery, then how it will create/update records in CMDB?

If You don't configure IRE rule  first thing is it define OOB And second thing I have notice while you create a record manually in CMDB table it will not check for IRE  and cause lots of issue like The system will likely struggle to uniquely identify CIs, potentially leading to duplicate entries in the CMDB. which is not good practice and your CMDB is not healthy.

for better understanding about IRE check below links

https://www.servicenow.com/community/cmdb-articles/understanding-ire-reconciliation-rules/ta-p/32892...

https://servicenowwithrunjay.com/identification-and-reconciliation/

if my answer helps you mark helpful and accept solution

[AJ-TechTrek]

Hi @Lucky1 ,

Lets ,Recap of how it works (in plain language):

* Identification rules: Figure out which record (CI) to create or update by comparing incoming data to existing CIs.
* Reconciliation rules: Decide which data source can update which fields in the CI when there is a conflict (multiple sources reporting).

First Question:
Is it like Identification rule will create a record?
Answer:
* Yes and no — let’s clarify:
* The Identification Rule itself doesn’t directly create a CI.
* Instead, when ServiceNow Discovery (or an Import, or Integration) sends data, the IRE engine:
1. Applies the Identification Rule → it checks if a CI with matching identifiers (e.g., serial number, name, FQDN) already exists.
2. If a matching CI is not found, the IRE will create a new record in the CMDB.
* So, the process creates the record; the Identification Rule tells IRE how to do the matching.

Second Question:
If the record exists, does the Identification rule update the record, or does the Reconciliation rule do that?
Answer:
* Identification Rule: only tells IRE which CI to work on (find existing or create new).
* Reconciliation Rule: decides what fields the incoming data is allowed to update.
* So, the sequence:
1. IRE uses the Identification Rule → locates the correct CI (or creates it).
2. Then, if the CI already exists → Reconciliation Rule checks if the incoming data source is authorized to update specific fields.
* So the update only happens after passing the Reconciliation Rules.

Third Question:
Reconciliation rules come into picture if there are more than one data source, and they only update records, not create them. Is this correct? If so, why?
Answer:
* Correct!
* Reconciliation Rules:
* Are used only when multiple sources can update the same CI.
* They tell IRE which data source can update which field on an existing CI.
* They do not create new records because creating a CI is always based on Identification Rules.
* Why? Because:
* Identification (matching/creating) must happen first.
* Reconciliation is about conflict resolution → when data sources send different values for the same field.

My Last Question:
If we don’t configure IRE rules, and we run discovery, how does it create/update records?
Answer:
* If you don’t configure custom IRE rules:
* ServiceNow still uses out-of-the-box Identification Rules for standard CI classes (e.g., cmdb_ci_computer, cmdb_ci_win_server).
* If you remove all Identification Rules for a CI class:
* IRE won’t know how to match → incoming data won't insert/update properly → CIs may not be created or updated.
* Discovery requires Identification Rules to work properly.
* Without Reconciliation Rules:
* All fields might get updated by any data source → leading to data conflicts and quality issues.
* But by default, out-of-the-box rules are there; you need custom rules mainly for custom classes or special scenarios.

Please appreciate the efforts of community contributors by marking appropriate response as Mark my Answer Helpful or Accept Solution this may help other community users to follow correct solution in future.
 
Thank You
AJ - TechTrek with AJ
LinkedIn:- https://www.linkedin.com/in/ajay-kumar-66a91385/
YouTube:- https://www.youtube.com/@learnitomwithaj
ServiceNow Community MVP 2025

[Sangeeta Das]

super helpful and clear explanation of IRE in simple language. Your videos are good as well. lot of information in ITOM Batch 1, 2 and 3 videos!

[AJ-TechTrek]

Thanks you so much for your feedback @Sangeeta Das . Please share reference of Youtube who want to learn ITOM.

Thanks

AJ- TechTrek with AJ

[Lucky1]

Hello all,

I have seen Identifier record on Hardware (cmdb_ci_hardware) table, and few identifier entries. But there are no Reconciliation rules defined for this table. 

When I check the Hardware table list view, Updated by field is "Middiscovery" and now I have these below 2 questions:

1. If there are only Identifier entries created and no reconciliation rules defined, then how the attributes in the class that got identified will be updated?

2. Secondly, if a class is identified by criterion attributes in the identifier entry record, then which all attributes of the class will gets updated and more importantly, where we can find that information in the system?

Please help,

Regards,

Lucky