Fragmenting Large Transmissions
HL7 does not support a generic mechanism to fragment large messages. Any fragmentation for transmission/transport purpose should be dealt with within the Messaging Infrastructure Layer. The receiving HL7 Application has the option of refusing an interaction because of its size.
Fragmentation is present in v2 (in the form of the DSC segment, as a site negotiation option). The concept is problematic in HL7 v3: fragmentation is a post-serialization ITS specific issue.