EMS Manual

Collector Event Messages
EMS Manual—426909-005
20-31
524: ZEMS-EVT-LOGTIME-DECREASE
ZEMS-TKN-SUBJECT-MARK (shared)
is the standard EMS token that immediately precedes each subject token. This
event message has one subject token:
ZEMS-TKN-COLLECTOR (nonshared)
specifies the collector type. This token has one of two values: ZEMS-SUBJ-
PCOLL (or 1) for the primary collector, or ZEMS-SUBJ-ACOLL (or 2) for the
alternate collector.
ZEMS-TKN-OLD-LOGTIME (nonshared)
is the log time (Julian timestamp) of the event message logged just before a
system-time change.
ZEMS-TKN-NEW-LOGTIME (nonshared)
is the log time (Julian timestamp) of the event message logged just after a system-
time change.
Cause. The log timestamp of a just-received event message is out of sequence. This
sequence of events describes conditions that can cause an ZEMS-EVT-LOGTIME-
DECREASE message to be issued:
1. The collector is writing event messages to the current log file. It puts a log
timestamp in each message. This is an example timestamp:
Event A (19:00)
2. The collector compares the log timestamp of each message to that of the
preceding message. If each timestamp is greater (later) than that in the previous
message, the messages appear in the order expected by the collector, and logging
continues. In the following, event B is an example of a greater (later) timestamp:
Event A (19:00) ... Event B (19:01)
3. The system operator resets the system time to an earlier time, using a SETTIME
command.
4. The collector timestamps the next event message:
Event C (18:58)
This strategy creates a temporary reversal in the sequence of timestamps. (If the
system time is reset to a later value, there is no problem.)
5. The collector compares this timestamp to the timestamp of the previous message
and determines that the timestamp of the current message is less (earlier) than the
timestamp of the previous message. In this example, event C has an earlier
timestamp:
Event B (19:01) ... Event C (18:58)