In an XCS network, the time management of BS2000 includes two additional functions for time synchronization:
synchronization of the clocks of the processors in the XCS network
an XCS-wide, strictly uniformly advancing time, called the XCS time.
While the first function largely guarantees identical times on all of the processors in the XCS network and prevents discrepancies developing in the system times caused by the system clocks running at different speeds, the second function offers the option of relating globally to a shared time.
The time synchronization functions are a standard component of every XCS network. They are implemented by the DSSM subsystem XCS-TIME which is started and terminated under the aegis of the XCM (registered function XTS).
The time synchronization is initialized when an XCS network is started or when a processor enters an XCS network.
To achieve the time synchronization of the processors in the XCS network, the computer-local times are exchanged via the DLM. The XTS function initiates the exchange of time information at periodic intervals. The exchange of time information is therefore independent of any lock exchange. This means that good synchronization of the system times can be achieved and the differences are usually a matter of less than a second.
If no processor has a radio clock connection, the network time in the XCS network is defined by the processor that has the fastest running clock. The clock time of the processors with the slowest running clocks is adjusted accordingly.
If one of the processors has a radio clock connection, the entire network is synchronized according to the radio clock time.
If all participants have a radio clock connection, time synchronization no longer takes place. XCS-TIME checks only the time differences and, if necessary, initiates a network exit if the time differences become too great, e.g. because of a defective radio clock.
connection. Processors without a radio clock attempt to keep in line with processors with a radio clock. However, if the times of the various radio clocks arrive in the wrong order, e.g. owing to problems in the BCAM network, the synchronization requests can be contradictory and lead to errors.
The information as to whether processors have a radio clock connection is provided as a status display in the GTIMR interface and in the output field SYNCHRONIZATION of the SHOW-SYSTEM-INFORMATION command.
In addition to the synchronized system time, the XCS time is also executed on every processor in the XCS network. This XCS time applies uniformly to all the processors when they are queried under the same (distributed) lock. The XCS time can therefore be used for logging entries with a counter with UTC time semantics.
For the user, the XCS time is accessible via the GTIME interface (XCS_MODE=*YES) (see the manual "Executive Macros" [12 (Related publications )]).
the underlying internal time coordinate UTC, which corresponds to Greenwich Mean Time. Identical GTIME parameters result in identical local times. However, it is possible to set different local times on the XCS network participants by specifying different ZONE, DIFF or CHDATE values in the GTIME parameter set. Conversely, the network entry of a processor will be rejected despite the identical local time if the internal time coordinate UTC on it is different and the difference has merely been “corrected” by means of correspondingly adjusted GTIME parameters.