Time management TODR correction values have the followings aims:
The system time can be adapted to external timers or to a network time without modifying the TODR; this makes it possible to put the system time back.
It shifts the system time without affecting the TODR on summer time/winter time changeovers
It is particularly important not to put back the TODR while the system is running, since many algorithms in the operating system and application software are based on the unbroken ascending incrementation of the TODR.
Whenever a system time synchronization job is concluded, the currently valid TODR correction value is increased by this job value if the time is put back or decreased by this value if the time is put forward. Declared real time timers (STXIT or system-internal) are adapted accordingly. When the current system time is provided in a GTIME, GDATE or GETOD, the current TODR correction value is taken into account.