gtps4m23System Generation

System Clocks

TPF operates using the time-of-day clock (TOD) to manage various system functions such as subsystem clock update. Upon initial IPL of TPF, the system operator will be requested to set the correct TOD value if the TOD clock is not operating.

Users of the HPO feature and the loosely coupled facility are required to install either the clock synchronization RPQ or a Sysplex Timer (STR), so that all processors in the LC complex will run their TOD clocks with the same value. The synchronization is done upon system restart.

Note:
The IBM 9037 Sysplex Timer is part of the IBM Enterprise Systems Connection Architecture.

The TOD clock itself is not used for application programs. TPF provides software clocks for their use. These software clocks are managed as a delta to the TOD clock. The initial values of the various software clocks are provided via the SIP CLOCKS macro.

The user must provide the calendar starting time of the system, along with the local and Greenwich Mean Time (GMT). For HPO feature users of the multiple database function (MDBF), the user must provide a CLOCKS macro for each subsystem being generated, plus an additional parameter (DELTIM) that specifies the subsystem difference (delta) from the system clock.

Note:
The BSS clocks also operate on the basis of a delta from the TOD clock even without the use of MDBF.