To clarify, if we did knock the EIS name down to an int/short as Mark indicated was feasible. We would have the following:
byte[]:64:bqual {Uid:28:sequenceId,String:variableLength:subordinateNodeName,String:variableLength:parentNodeName,int/short:4/2:EISName}
Meaning we would still need to be able to get two strings into the remaining 34/32 bytes, another reason I suggested converting the node name in the AS down to an int as that saves the space of two strings rather than just one.
Plus the API for getting the EIS name is already out there and is being used (I assume). We would therefore need to get folks to change their implementation of: org.jboss.tm.XAResourceWrapper::getJndiName to return this integer key for the EIS name table (or pay the cost of looking up this String in the EIS String to int table each time and XID is created).
Either approach (keying node names or keying EIS names) levies an administration overhead but for space considerations and the fact that the EIS name API is already out there I think we should use ints in the XID for nodes rather than EIS names - again though, happy to be dissuaded.