When is a Profile Change Active? 
Purpose
When you modify profile parameters using the profile maintenance tool, the changes do not take effect immediately in the associated R/3 instance. The characteristics of an R/3 instance cannot be changed during active operation.
Process Flow
To activate the changes
Checking, Saving and Activating Profiles

An active profile that already exists in the R/3 System is backed up automatically. A backup file is created with the extension .bak . You can copy and display this backup file even if the R/3 System is not available.
See also:
Checking the Operation Mode with the Control Panel Operation Modes and Instance Definitions: Contents System Monitor