HL7 Sequence Numbering Protocol

The Adapter can be configured to use HL7 sequence numbering. The negotiation and incrementation of this number is automatically performed by the Adapter. For more details on HL7 sequence numbering, refer to Appendix C (Lower Layer Protocols) of the HL7 Standard for the HL7 version you are using.

When the Adapter is configured for HL7 sequence numbering, the sequence number file opens when the Adapter starts up. If the sequence number file does not exist, one is created and populated with a zero sequence number. The sequence number file is updated on the inbound Adapter when the Adapter generates the HL7 ACK (this process is transparent to the user), and when the outbound Adapter receives the HL7 ACK from the external system.

If you want to change the sequence number at runtime, you need to suspend the Adapter, edit and save the sequence number file, and reactivate the Adapter. To force the Adapter to resynchronize its sequence number with the external system, you need to suspend the Adapter, edit the file so it contains a “-1”, and then reactivate the Adapter.

The minimum HL7 sequence number is 1. The maximum HL7 sequence number is 2 billion. A sequence number of “0“ is used to start a session. If the sequence numbers between the Adapter and the external cannot be reconciled during start or when exchanging messages, the Adapter shuts down and wait for human intervention as dictated by the HL7 Standard.