Force.com IDE Developer Guide

Get Started with the Force.com IDE
Develop with the Force.com IDE
Test Code with the Force.com IDE
Deploy Code with the Force.com IDE
Get Started with the Apex Debugger
Get Started with the Apex Debugger
Set Up the Apex Debugger
Contact Salesforce to Enable the Apex Debugger
Install or Update the Force.com IDE Plug-In for Eclipse
Set Up a Permission Set
Create a Project
Test Your Debugger Setup
Whitelist Users and Request Types
Explore a Simple Debugging Puzzle
Manage Debugging Sessions
Apex Debugger Limits and Considerations
Apex Debugger Troubleshooting
Get Started with the ISV Customer Debugger
Solutions to Common Force.com IDE Problems
Force.com IDE Release Notes
Useful References
PDF

Contact Salesforce to Enable the Apex Debugger

Some services and subscriptions include the debugging feature for an extra cost. For pricing details, contact your Salesforce account executive. After Salesforce grants licenses for the Apex Debugger to your production org, match your production license counts to your sandbox.
Available in: both Salesforce Classic and Lightning Experience
Available in: Enterprise, Performance (one session included), and Unlimited (one session included) Editions

User Permissions Needed
To match licenses to sandbox: Modify All Data

The matching process updates the license counts in your sandbox so that they match production. The process adds licenses to your sandbox that are in production but not in your sandbox, and deletes licenses from your sandbox that aren’t in production.

To match licenses to a sandbox org, log in to your sandbox org. From Setup, enter Company Information in the Quick Find box, then select Company Information | Match Production Licenses. This process triggers an alert informing you that the matching process has started. After all licenses have been matched in sandbox, a confirmation email is sent to you. The confirmation email is always sent to the user who initiates the license copy.

Matching production licenses requires that your sandbox and production orgs are on the same Salesforce release. If your sandbox has already been upgraded to the next release but production hasn’t been upgraded (for example, during sandbox preview), you can’t match production licenses in sandbox.