initial program load (OS) (IPL)
Initial Program Load (IPL) is a term from the mainframe world that describes the restart of an operating system of mainframes.
The IPL process is similar to bootingpersonalcomputers. Restarting operating systems was time-consuming in that program codes with a character count of many megabytes had to be loaded into main memory. When configuration changes were made, the system had to be shut down and the configuration files changed. With today's systems, reconfigurations take place dynamically during operation.