When a user logs in.

When a user logs in, the system will process their .profile file which contains the PATH variable. This variable specifies the list of directories that the system will search through to locate executable files. If the PATH variable contains non-existent directories, then it will take longer for the system to process the .profile file, resulting in a slower login experience. Reference: IBM AIX v7 Administrator Specialty Study Guide (page 9-10).