C$UNSET
The C$UNSET library routine removes a variable from the environment.
It can be used to remove any configuration setting except for keystrokes. Keystrokes cannot be initialized to their defaults by calling C$UNSET, they must be reset using a Format 6 SET statement, setting them to the proper value as described in 
Default Keyboard Configuration. 
Syntax:
 CALL "C$UNSET" USING envVarName  | 
Parameters:
envVarName  | PIC X(n)  | Specifies the environment variable to be removed.  | 
Examples:
Example - Remove custom property my.report.path
call "c$unset" using "my.report.path"  |