Q: What causes ServiceNow Instance Running Slow?

Business Rule with expensive query in loop — Navigate to System Definition > Business Rules and check recently modified rules. Look for GlideRecord queries inside while loops, especially on high-volume tables like incident, task, or user records. Missing database index on large table — Check System Diagnostics > Stats > Table Stats for tables with high row counts. Look for tables over 100k records without proper indexes on frequently queried fields like state, assigned_to, or custom fields. Client Script making excessive GlideAjax calls — Open browser Developer Tools Network tab and check for repetitive AJAX calls on form load or field changes. Navigate to System Definition > Client Scripts and look for onChange scripts with GlideAjax calls. Scheduled Jobs running during peak hours — Navigate to System Scheduler > Scheduled Jobs and check execution times. Look for data imports, reports, or cleanup jobs scheduled during business hours (8 AM - 6 PM). Unoptimized recent deployment code — Check System Update Sets > Retrieved Update Sets for recent deployments. Review any new Script Includes, Business Rules, or Workflows that may contain inefficient GlideRecord queries or missing encoded queries.

Question 1

What causes ServiceNow Instance Running Slow?

Accepted Answer

Business Rule with expensive query in loophigh likelihood

Navigate to System Definition > Business Rules and check recently modified rules. Look for GlideRecord queries inside while loops, especially on high-volume tables like incident, task, or user records.

Missing database index on large tablehigh likelihood

Check System Diagnostics > Stats > Table Stats for tables with high row counts. Look for tables over 100k records without proper indexes on frequently queried fields like state, assigned_to, or custom fields.

Client Script making excessive GlideAjax callsmedium likelihood

Open browser Developer Tools Network tab and check for repetitive AJAX calls on form load or field changes. Navigate to System Definition > Client Scripts and look for onChange scripts with GlideAjax calls.

Scheduled Jobs running during peak hoursmedium likelihood

Navigate to System Scheduler > Scheduled Jobs and check execution times. Look for data imports, reports, or cleanup jobs scheduled during business hours (8 AM - 6 PM).

Unoptimized recent deployment codemedium likelihood

Check System Update Sets > Retrieved Update Sets for recent deployments. Review any new Script Includes, Business Rules, or Workflows that may contain inefficient GlideRecord queries or missing encoded queries.

Question 2

How do you fix ServiceNow Instance Running Slow?

Accepted Answer

How to fix it Navigate to System Diagnostics > Stats > Slow Queries to identify the most expensive database queries running on your instance. Check System Definition > Business Rules and filter by Updated field for rules modified in the last 30 days. Open each recent Business Rule and search for while loops containing GlideRecord queries. This is the most common cause of performance issues. For any problematic Business Rules, either optimize the query with addEncodedQuery() or move the logic outside the loop. Consider using setLimit() to prevent runaway queries. Navigate to System Diagnostics > Stats > Table Stats and identify tables with high record counts (>100k) that appear in your slow queries. Go to System Definition > Tables and open the problematic table. Click the Database Indexes related list to review existing indexes. Create new indexes for frequently queried fields by clicking New in the Database Indexes section. Focus on fields used in WHERE clauses of your slow queries. Check System Definition > Client Scripts for onChange scripts. Open browser Developer Tools and monitor Network tab while loading forms to identify excessive AJAX calls. Optimize Client Scripts by adding conditions to prevent unnecessary GlideAjax calls, or consolidate multiple calls into a single Script Include method. Navigate to System Scheduler > Scheduled Jobs and review jobs scheduled between 8 AM and 6 PM. Move resource-intensive jobs to off-peak hours. Review recent update sets in System Update Sets > Retrieved Update Sets for any new code that may contain inefficient queries or missing encoded query parameters.

Question 3

How do you prevent ServiceNow Instance Running Slow?

Accepted Answer

Enable the Business Rule performance analyzer in System Properties > Performance by setting glide.businessrule.debug to true to catch expensive rules before they impact users. Implement code review guidelines requiring addEncodedQuery() and setLimit() on all GlideRecord queries, especially in Business Rules and Script Includes. Schedule all data imports, reports, and cleanup jobs during off-peak hours (10 PM - 6 AM) using the System Scheduler conditional execution feature. Create database indexes proactively on custom fields that will be used in list filters, reports, or integrations before going live. Set up automated monitoring using System Diagnostics > Performance Analytics to alert when average page load times exceed 3 seconds.

ServiceNow Instance Running Slow

Symptom

Possible Causes

Debugging this in a real instance?

Solution

How to fix it

Prevention Tips

Test Your Knowledge