ServiceNow Best Practices: Data Transfer with g_scratchpad: A Guide for ServiceNow Developers
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02-02-2025 03:08 AM
Introduction: For ServiceNow developers, efficiently passing data from the server to the client is essential to ensure optimal form performance and user experience. This article focuses on the g_scratchpad object, a tool provided by ServiceNow display Business Rules to transfer data that may not be directly available on a form. We'll cover its benefits, how it works, and when to use alternative approaches such as asynchronous GlideAjax calls.
What is the ServiceNow g_scratchpad Object? The g_scratchpad object is a client-accessible storage object created by a display Business Rule. It allows developers to pass information from the server to the client-side before the form is loaded. This is particularly useful when client scripts need data that is not present on the form.
For example, if a Client Script requires access to the assigned_to field, but that field is not displayed on the form, the script cannot access it. One solution is to add the field to the form and hide it using a Client Script or UI Policy, but this approach increases form load time and complexity.
Instead, using a display Business Rule to populate g_scratchpad is more efficient and secure.
Key Characteristics of the ServiceNow g_scratchpad Approach:
Execution Timing: Data is prepared on the server before the form is displayed to the user.
Data Sharing: The g_scratchpad object is available to all client-side scripts, ensuring that necessary information is ready on form load.
Efficiency: Unlike dynamically triggered server calls, this method reduces network traffic by preloading data.
When to Use g_scratchpad vs. GlideAjax:
Use g_scratchpad: When you know the client will need certain information before the form is loaded.
Use GlideAjax: For dynamic interactions that require additional server data after the form is loaded.
Display Business Rules cannot trigger dynamically during a session. In scenarios requiring real-time server communication, asynchronous GlideAjax calls provide a more flexible solution.
How to Create a ServiceNow Display Business Rule:
Navigate to System Definition > Business Rules.
Click New and fill out the form:
Name: Provide a descriptive name (e.g., "Populate Scratchpad for Incident Form").
Table: Select the relevant table.
When to Run: Set it to Display.
Use a script to define the g_scratchpad properties with the required data.
Common Use Cases:
Dynamic Form Enhancements: Preload configuration data to enable form customization.
Security: Prevent unauthorized data exposure by filtering data on the server.
Performance Optimization: Reduce redundant server calls by providing necessary data at load time.
Tips for Developers:
Minimize the amount of data added to g_scratchpad to improve performance.
Test both form load and client-side behavior to ensure smooth functionality.
Document your display Business Rules to help maintain clear dependencies between server-side and client-side logic.
Conclusion: For ServiceNow developers, the g_scratchpad object is a powerful feature for transferring essential data to client scripts. By leveraging display Business Rules effectively, you can enhance performance, improve data security, and streamline form interactions. Understanding when to use g_scratchpad versus other server-client communication methods is key to building scalable and maintainable applications.
Watch a Live Example: See how to implement g_scratchpad effectively in a live demonstration on my YouTube channel!
Feedback: We’d love to hear from you! Share your thoughts or questions about this guide in the comments or connect with the ServiceNow developer community.
