regarding one to one relationship of SIR to Digital IT

[Siva_Prasad]

we want to have only one to one relationship of SIR to Digital IT  , can I get the solution for this to establish this relation?

[MaxMixali]

ServiceNow – Enforcing One-to-One Relationship Between SIR and Digital IT

Scenario
You need to ensure a one-to-one relationship between Security Incident Records (SIR) and Digital IT records in ServiceNow — meaning:
- Each SIR can be related to only one Digital IT record.
- Each Digital IT record can be related to only one SIR.

This relationship must be enforced at the data model and UI levels.

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1. Define a Custom Relationship Type
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1. Navigate to: Configuration → Relationships → CI Relationships Types.
2. Create a new relationship type, for example:
- Parent Class: Security Incident (sn_si_incident)
- Child Class: Digital IT Service (cmdb_ci_service_digital)
- Name: Secures / Secured By
3. Ensure both classes are correct for your environment.

This defines the logical link between the two record types.

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2. Enforce One-to-One Cardinality (Business Rule)
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ServiceNow does not enforce one-to-one relationships natively, so use a Business Rule to restrict creation of additional relationships.

Table: cmdb_rel_ci
When: Before Insert
Condition: type.name = your relationship type name

Example Business Rule Script:

(function executeRule(current, previous /*null when async*/) {
// Check existing relationships from the SIR side
var relFrom = new GlideRecord('cmdb_rel_ci');
relFrom.addQuery('parent', current.parent);
relFrom.addQuery('type.name', 'Secures'); // Replace with your relationship name
relFrom.query();
if (relFrom.hasNext()) {
gs.addErrorMessage('A Security Incident can be related to only one Digital IT record.');
current.setAbortAction(true);
return;
}

// Check existing relationships from the Digital IT side
var relTo = new GlideRecord('cmdb_rel_ci');
relTo.addQuery('child', current.child);
relTo.addQuery('type.name', 'Secures');
relTo.query();
if (relTo.hasNext()) {
gs.addErrorMessage('A Digital IT record can be related to only one Security Incident.');
current.setAbortAction(true);
return;
}
})();

This rule aborts any insertion if a relationship already exists on either side.

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3. Optional – Add a Client Script or UI Policy
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To enhance UX, you can hide or disable the “Add Relationship” option when one already exists.

Example Client Script (onLoad):

function onLoad() {
var sir = g_form.getValue('sys_id');
var ga = new GlideAjax('RelationshipCheckUtils');
ga.addParam('sysparm_name', 'hasExistingDigitalIT');
ga.addParam('sysparm_sir', sir);
ga.getXMLAnswer(function(resp) {
if (resp == 'true') {
g_form.setReadOnly('digital_it_reference_field', true);
g_form.showFieldMsg('digital_it_reference_field', 'This Security Incident already has a Digital IT link.', 'info');
}
});
}

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4. Script Include for Relationship Check
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var RelationshipCheckUtils = Class.create();
RelationshipCheckUtils.prototype = Object.extendsObject(AbstractAjaxProcessor, {
hasExistingDigitalIT: function() {
var sir = this.getParameter('sysparm_sir');
var gr = new GlideRecord('cmdb_rel_ci');
gr.addQuery('parent', sir);
gr.addQuery('type.name', 'Secures');
gr.query();
return gr.hasNext();
}
});

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5. Testing
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- Try linking multiple Digital IT records to one SIR → should be blocked.
- Try linking one Digital IT record to multiple SIRs → should be blocked.
- One-to-one link → allowed.

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Summary
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✅ To establish and enforce a one-to-one relationship:
1. Create a custom relationship type between SIR and Digital IT.
2. Add a Before Insert Business Rule on cmdb_rel_ci to block duplicates.
3. Optionally, add a Client Script or UI Policy for a better user experience.
4. Maintain integrity via a reusable Script Include for checks.

This ensures strict one-to-one data integrity between Security Incident and Digital IT service records.