Full and delta instance scans
Summarize
Summary of Full and Delta Instance Scans
The full and delta instance scan feature in ServiceNow allows administrators and developers to efficiently initiate, monitor, and manage instance scans from the Scan Results list view. The system automatically selects between a full or delta scan based on the instance's scan history, ensuring optimized scan performance while safeguarding instance resources through enforced concurrency rules. Real-time visibility into scan status and contextual notifications keep users informed throughout the scan lifecycle.
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Key Features
- Intelligent Scan Initiation: The Initiate Scan button determines whether to run a full or delta scan automatically, minimizing user decision-making.
- Force Full Scan: Administrators can override an ongoing scan to start a full instance scan immediately, providing flexibility when a comprehensive scan is necessary.
- Real-Time Scan Status: Users receive up-to-date indicators on scan progress, including states such as in progress, queued, complete, or cancelled.
- Scan Cancellation: The ability to cancel in-flight or queued scans enhances control over resource usage and scan scheduling.
- Safe Concurrency: Update Set Scans and Application Scans can run concurrently with full instance scans without causing conflicts or resource contention.
Concurrency Rules and Behavior
- The first scan on an instance triggers a full scan; subsequent scans default to delta scans.
- Only one full instance scan can run at a time to prevent excessive resource load; additional full scan requests are blocked with alerts.
- If a scan is in progress, initiating a delta scan is blocked with a notification; administrators can use the Force Full Scan option to override.
- Force Full Scan cancels any ongoing scan and immediately starts a new full instance scan.
- Update Set Scans and Application Scans are allowed to run in parallel alongside full scans.
User Notifications and Interface
- Users receive clear, contextual messages when scans are triggered, blocked, or require confirmation to override.
- A confirmation modal appears when forcing a full scan during an active delta scan, ensuring intentional user actions.
- The Scan Results list view displays key scan metadata such as scan number, start time, scan type, status, and scan engine score.
- Users must refresh the Scan Results list view to see the most current scan status updates.
Access Control
- Admin Role: Can initiate scans and use the Force Full Scan option.
- AI Fix User: Can initiate scans but not force full scans.
- Scan User and Read User: Have view-only access with no ability to initiate scans.
This role-based access ensures appropriate control over scan operations according to user responsibilities.
The full and delta instance scan feature enables ServiceNow administrators and developers to initiate, monitor, and manage instance scans directly from the Scan Results list view.
The system intelligently determines whether to run a full or delta scan based on instance history, while enforcing concurrency rules to protect instance performance. Administrators receive real-time scan-state visibility and contextual notifications at each stage of scan execution, from initiation and queuing to completion or cancellation.
- Initiate Scan: Intelligently determines the scan type as whether to run a full or delta scan based on instance history, reducing user decision-making burden while optimizing scan efficiency.
- Force Full Scan: Administrators retain the ability to override an in-progress scan when a complete instance scan is needed instead of a delta scan, providing flexibility while maintaining resource control.
Users gain visibility into whether their scan was initiated, queued, or blocked preventing repeated scan execution requests, but, resulting in no actual scan being executed. The system intentionally restricts users from running multiple full instance scans in parallel. Scan status is prioritized with visibility to the primary users with an indication of scan state preventing repeatedly attempted scan execution.
Key capabilities
- Real-time status visibility: Clear indicators showing scan states (in progress, queued, complete)
- Scan cancellation: Ability to cancel in-flight scans or queued requests
- Safe concurrency: Update Set Scans and Application Scans can execute while full scans are running
Concurrency rules and scan behavior
Full and Delta scan supports update set scans and application scope scans. The Scan Engine enforces specific concurrency rules to protect instance performance and manage resource allocation:
- First scan behavior: If the instance does not have any prior full scan, selecting Initiate Scan triggers a Full Instance Scan. Consecutive scans will be Delta Instance Scans.
- In-progress alerts: If a scan is already in progress, attempting to initiate another scan displays an alert: "Cannot initiate a delta scan while another scan is in progress. Wait for the current scan to complete or use Force Full Scan to override."
- Full Instance Scan blocking: Only one Full Instance Scan can run at a time. The system prevents parallel full scans to avoid excessive resource load. Additional full scan requests are blocked with an alert message.
- Force Full Scan override: Administrators can use the Force Full Scan button to cancel the current scan and immediately start a new Full Instance Scan. The current scan is cancelled automatically, and the new full scan is initiated.
- Parallel scan allowance: While certain scans run, Update Set Scans and Application Scans can still execute concurrently without blocking.
- Scan status visibility: Users can see scan states in real-time on the Scan Results list view, including "Getting ready," "Complete," and "Cancelled" status indicators.
User notifications and status indicators
The system provides contextual notifications and visual indicators to keep users informed:
- Scan triggered message: When a scan is successfully initiated, users see: "A new scan has been triggered and it will take a moment to reflect in the queue. Refresh the page for the latest scan results."
- Scan in progress alert: When attempting to initiate a scan while one is already running, an alert displays: "Cannot initiate a delta scan while another scan is in progress. Wait for the current scan to complete or use Force Full Scan to override."
- Trigger Scan modal: When using Force Full Scan while a Delta Scan is in progress, a confirmation modal appears with the title "Trigger Scan" and message: "A Delta Scan is currently in progress. Do you want to cancel the ongoing Delta Scan and start a Full Scan instead?" Users can select OK to proceed or Cancel to terminate.
- Real-time updates: The Scan Results list view displays scan metadata including Number (PSR#), Start Time, Scan Type (Full Instance Scan, Delta Instance Scan, On Demand Instance Scan), Status, and Scan Engine Score.
Access control by persona
Scan initiation capabilities are determined by user roles:
| Role | Permissions |
|---|---|
| Admin | Initiate scans and Force Full Scan |
| AI Fix User | Initiate scans only |
| Scan User | No scan initiation buttons (view only) |
| Read User | No scan initiation buttons (view only) |