Ensemble HL7 Version 2 Development Guide - InterSystems ...

Elements of a Routing Production
LargeGapSize
• MSH:10 MessageControlId
A sequence manager can check for duplicate messages and messages out of sequence,
duplicate messages or messages out of sequence, or neither. This makes EnableDuplicatedMessageCheck
entirely independent of PerformSequenceNumberCheckOn in that either, one, or
both of these settings may be True.
A number that indicates a significant gap in the sequence of messages.
A late message is a message that arrives with a sequence number larger than the previously
received message in the sequence, but not exactly sequential. For example, when message
102 arrives after message 101, 102 is not late; it is the next message in sequence. However,
when message 110 arrives after message 101, 110 is a late message.
When there is a late message, and the sequence numbering gap between the preceding and
subsequent messages is less than the configured LargeGapSize, this is a small gap. A gap
larger than this is a large gap.
• For any small gap, the sequence manager waits for MessageWaitTimeout seconds to see
if messages will arrive to fill the gap. If the messages arrives within the waiting period,
the sequence manager aligns them in their proper sequence. If they do not arrive and the
MessageWaitTimeout expires, the sequence manager stops waiting and sends whatever
it has for messages in the current sequence.
• When there is a large gap, the sequence manager does not wait for any period of time.
It immediately sends an alert, then sends whatever it has for messages in the current
sequence.
The default LargeGapSize is 100.
MessageResendableTimeWindow
Time window during which the sequence manager considers a duplicate message to be a
duplicate. The reason for the MessageResendableTimeWindow is that sometimes a duplicate
message is not a mistake. Sometimes it is the result of deliberately resending a message
sequence.
Suppose a message arrives and the sequence manager detects that it is a duplicate of a previously
received message. In this case:
• If it has been more than MessageResendableTimeWindow seconds since the sequence
manager first saw this message, it interprets the new arrival as a deliberately resent copy.
The sequence manager begins tracking the messages in this resent sequence independently
from its tracking of the main sequence of messages.
40 Ensemble HL7 Version 2 Development Guide