Theo van Veen wrote:

> I missed this point. Are reference id's used by the client to keep session context or by the server?

Z39.50 reference ids, and session ids, are so different that I hesitate to prolong any discussion of
reference ids. Sorry I raised the comparison.

But in answer to your question, they aren't used to keep session context, if by session you mean
Z-association.  Rather, they are used to keep operation context (by both the client and server) and are
useful when there are concurrent operations (more than a single concurrent operation within a
z-association, see 3.4 and 3.5 of the standard). Their usefulness outside of concurrent operations is
undefined by the standard.